Search Results (93)

Among the ferromagnetic shape memory alloys (SMAs), Ni43Mn31Ga19Co7 (at%) alloys are well known as a promising ferromagnetic SMA (FeSMA) for magnetocaloric effect, and scientific interest has increased due to the possible exploitation of multicaloric function. This first example of multi-effect by coupling elastocaloric and magnetocaloric effect is still far from complete experimental validation, mainly due to the difficulty of testing conditions that require the simultaneous application of both fields. In this study, a low magnetic field (μ₀H = 0.26 T and 0.56 T) is applied during elastocaloric deformation at different temperatures. Although the magnetic field values applied in this work are much lower than those usually considered in the magnetocaloric effect, the magnetic field improves the elastocaloric effect, increasing the total strain and reducing the critical stress and mechanical hysteresis. This synergic action allows us to obtain an increase in the ΔT_ad of about 13% and 25% upon loading and unloading, respectively. Full article

Background: While live-cell therapies face significant translational hurdles, cell-free secretomes derived from fetal progenitor cells offer a unique, scalable approach natively programmed for scarless tissue repair. Methods: This GLP-compliant study evaluated the therapeutic efficacy spectrum of an off-the-shelf, clinical-grade, intratracheal lyophilized FE002-Lu lung fibroblast conditioned medium (LFCM) across five controlled Wistar rat models of induced lung injury: bleomycin (5 mg/kg), asbestos (100 µg/rat), hyperoxia (100% oxygen exposure), silica (30 mg/rat), and lipopolysaccharide (LPS, 4 mg/kg). Following lung injury induction and symptom onset, symptomatic rats were randomized to receive intratracheal LFCM (low, mid, or high dose) or a vehicle control every 4 days for 28 days. Results: The intervention demonstrated an exceptional safety profile, maintaining 100% survival with no severe procedural toxicity across all cohorts. Across all study arms, LFCM effectively attenuated pulmonary inflammation, reducing pro-inflammatory markers (IL-1β, IL-6, TNF-α, and CINC-1) in bronchoalveolar lavage fluid. Concurrently, high LFCM doses consistently elevated the anti-inflammatory cytokine IL-10. Within the lung tissue, mid- and high doses significantly reduced key pro-fibrotic drivers, including TGF-β1, TIMP-1, WISP-1, and hydroxyproline. Treatments consistently decreased α-SMA expression and pro-fibrotic gene mRNA levels, mitigating pulmonary myofibroblast activation. This correlated with reduced Ashcroft scores and collagen deposition, thereby preserving lung architecture. Notably, the FE002-Lu LFCM treatment exerted a biphasic regulation of extracellular matrix turnover: it elevated Cathepsin-D and MMP-12 in the bleomycin arm to actively clear newly deposited fibrotic debris, while reducing these markers in the hyperoxia and LPS arms to prevent acute collateral degradation of the native lung matrix. In both particulate models (asbestos and silica), the LFCM mid-dose established an optimal therapeutic threshold, avoiding the localized secretome saturation and pro-fibrotic exacerbation occasionally observed at higher doses. Conclusions: Lyophilized FE002-Lu LFCM acts as a potent, pleiotropic biologic that effectively resolves acute pulmonary inflammation and arrests progressive fibrotic remodeling across multiple distinct in vivo models. By overcoming the cold-chain and delivery limitations inherent to pulmonary live-cell therapies, this stable, cell-free secretome represents a highly scalable, “off-the-shelf” candidate poised for non-invasive, aerosolized clinical translation. Full article

Hybrid shape-memory materials combining structural and magnetic functionalities offer new opportunities for tailoring functional responses through mechanical coupling between dissimilar phases. In this work, a NiTi/NiFeGa bilayer composite was fabricated by high-speed high-pressure torsion (HSHPT), a severe plastic deformation technique enabling the consolidation of dissimilar materials. Although the constituent alloys exhibit martensitic transformations separated by nearly 135 K in their initial states, the HSHPT-processed hybrid displays a single dominant calorimetric transformation despite the absence of measurable chemical interdiffusion, consistent with a cooperative transformation response promoted by strong interfacial mechanical coupling. The microstructure was investigated by scanning electron microscopy, while the martensitic transformation and magnetic properties were characterized by differential scanning calorimetry and magnetometry. SEM observations revealed a well-defined bilayer architecture with a sharp chemically distinct interface. Despite the absence of measurable interdiffusion, the hybrid exhibited a transformation enthalpy approximately twice that of the NiTi constituent (≈20 J g⁻¹ vs. ≈10.35 J g⁻¹), accompanied by a broader thermal hysteresis. The magnetic response was also modified, exhibiting reduced saturation magnetization and increased coercivity. These findings demonstrate that HSHPT provides an effective route for designing hybrid functional materials with tunable thermomechanical and magnetic responses through controlled interfacial interactions between chemically distinct phases. Full article

To investigate the influence of porosity defects and the strengthening effect of bonded iron-based shape memory alloy (Fe-SMA) plates, fatigue tests were conducted on defect-free, porosity-containing, and Fe-SMA-strengthened U-rib butt-welded specimens. A numerical model considering porosity defects and the bonded Fe-SMA plate was also established and validated against the experimental results. The results show that porosity defects significantly increased the local stress level near the crack. Under a load of 60 kN, the stress at the section 2 mm from the crack edge increased from 98 MPa to 139.5 MPa. Meanwhile, the fatigue life decreased from 260 × 10⁴ cycles to 127 × 10⁴ cycles. After Fe-SMA strengthening, the stress decreased to 75.59 MPa, and the fatigue life increased to 326 × 10⁴ cycles, which was 2.57 times that of the unreinforced defective specimen. The Fe-SMA plate did not change the fatigue crack propagation path but effectively slowed crack growth through local stiffness enhancement and activation-induced pre-compressive stress. Parametric analysis further showed that, among the investigated numerical cases, an activation temperature of 200 °C produced the largest predicted strengthening effect. Increasing the pore diameter from 0.5 mm to 2.0 mm reduced the reinforcement effect from 69.45% to 52.98%, and increasing the crack length from 10 mm to 50 mm reduced it from 65.41% to 35.53%. These results indicate that bonded Fe-SMA plates can effectively improve the fatigue performance of U-rib butt-welded joints with porosity defects, especially when applied before excessive crack growth occurs. Full article

Iron-based shape memory alloys (Fe-SMAs) have considerable potential for the active strengthening of concrete structures, yet convenient externally applicable non-destructive methods for identifying local fatigue damage under cyclic loading remain limited. To investigate the weak magnetic response of notched Fe-SMA and its correspondence with local damage evolution, static tensile tests and constant-amplitude fatigue tests were conducted on Fe-SMA specimens with a semi-circular notch. Weak magnetic signals were continuously monitored at a fixed point throughout loading, and surface magnetic-field scanning was performed after fracture. Under static loading, the magnetic signal evolved consistently with the deformation response. Under fatigue loading, the fixed-point magnetic signal exhibited a clear three-stage evolution corresponding to the development of residual deformation. Compared with deformation hysteresis loops, magnetic hysteresis loops contained richer information on local damage evolution. After fracture, abrupt changes in the scanned magnetic field coincided with the actual fracture location, and the magnetic anomaly gradually attenuated as the scanning path moved away from the notch. These results indicate that weak magnetic signals can effectively characterise the evolution of local fatigue damage in notched Fe-SMA, with the normal magnetic component showing greater sensitivity to damage localisation and state assessment. Full article

Iron-based shape memory alloy (Fe–SMA) rebars can generate internal prestress in cement-based members after restrained thermal activation; however, the temperature actually reached by embedded rebars in cracked UHPFRC is difficult to infer from exposed bar segments. This study investigates electrical resistance activation of 4% prestrained Fe–SMA rebars embedded in pre-cracked UHPFRC beams and clarifies the activation-control problem by combining thermocouple measurements with a calibrated two-dimensional electro-thermal simulator. Twelve beams (150 × 150 × 600 mm) containing either Dramix 3D or Dramix 4D hooked steel fibers were first loaded in three-point bending to a mid-span displacement of 4 mm. The 4D series reached a 9.47% higher average pre-cracking load, confirming that fiber geometry modified the cracked state before heating. During activation, the exposed rebar segment reached 200 °C after approximately 77 s, whereas the embedded working segment reached the same target only after approximately 213 s; at that moment, the exposed segment was already close to 350 °C. The calibrated simulator reproduced the target activation time with an error of approximately 3 s and visualized the localized heat transfer from Fe–SMA to UHPFRC. The results demonstrate that activation control based only on exposed-bar temperature may cause under-activation of the embedded reinforcement, and that direct internal temperature monitoring is required for reliable Fe–SMA activation in cracked UHPFRC members. Full article

Iron-based shape memory alloy (Fe-SMA) fibers can enhance cementitious composites through both crack bridging and thermally activated recovery stresses. Since fiber pull-out governs load transfer at the micro scale, understanding the combined effects of fiber geometry, inclination, and thermal treatment is essential. This study experimentally investigated the pull-out behavior of hooked-end Fe-SMA fibers embedded in high-performance concrete (HPC). A total of 54 ASTM C307-type briquette specimens were tested using single-hook (3D) and double-hook (4D) fibers at inclination angles of 60°, 75°, and 90° under ambient, 100 °C, and 200 °C conditions. Additional flexural, compressive, and direct tensile tests were conducted on plain HPC exposed to the same thermal regime. At ambient temperature, 4D fibers showed 50–70% higher peak pull-out forces than 3D fibers. Heating to 100 °C further increased pull-out resistance by about 6–17%, and the 4D-60-100 configuration achieved the highest performance. In contrast, exposure to 200 °C reduced pull-out resistance by about 5–12% below ambient values. Overall, a 60° inclination generally provided a better response, while 90° produced the lowest. The results confirm that moderate thermal activation combined with double-hook geometry is the most effective strategy for maximizing Fe-SMA fiber–matrix load transfer in HPC. Full article

TiNiFe shape memory alloy pipe couplings exhibit excellent radial recovery capability and therefore show great potential for pipeline fastening applications. In this study, the radial recovery stresses at different locations within a TiNiFe SMA pipe coupling were determined using a finite element inverse method. These stresses were subsequently applied as boundary conditions to establish a numerical model describing the fastening connection and pull-out process between the TiNiFe coupling and a TA18 tube. The effects of coupling wall thickness on the connection state and pull-out failure behavior were systematically investigated. The results indicate that the radial recovery stress increases monotonically with increasing wall thickness, although the growth rate gradually decreases. When the wall thickness ranges from 1.25 to 1.75 mm, the interfacial contact stress increases with thickness, thereby enhancing the fastening effect. However, when the thickness exceeds 1.75 mm, the intensified radial deformation of the inner convexes leads to a significant reduction in contact stress. The pull-out process of the assembly can be divided into three stages, namely the initial, intermediate, and final stages, during which the pull-out force first increases and then decreases with the evolution of the contact state. These findings provide a theoretical basis for the structural optimization and engineering application of TiNiFe SMA pipe couplings. Full article

Iron-based shape memory alloys (Fe-SMAs) are promising for structural retrofitting because of their low cost, corrosion resistance, and manufacturability. However, the effect of strain rate on the coupled thermo-microstructural evolution during cyclic training remains underexplored. In this study, samples underwent cyclic tensile training at quasi-static and impact strain rates. After each cycle, DSC was adopted to obtain transformation temperatures and enthalpies, and selected cycles were characterized by EBSD (KAM and IPF) to quantify phase fractions and variant statistics. Results show tensile loading shifts transformation temperatures, with the principal difference between regimes appearing in the evolution of martensite finish temperature. Under impact loading, the transformation enthalpy increases more rapidly (0.18 to 0.8 J/g in absolute value), and the driving force decreases more markedly by the fourth cycle (−0.0578 to −0.1117 J/g), indicating faster thermodynamic changes at high strain rates. Internal stress and dislocation storage accumulate faster under impact, lowering the effective stress (−17.01 MPa) for transformation and promoting martensite nucleation/growth. EBSD reveals increasing lattice distortion; in impact-trained samples, single-variant martensite and higher stored energy reduce interface resistance and enable elastic energy release, accelerating transformation and improving shape recovery. Full article

This study presents an experimental investigation into the seismic performance of seismically deficient reinforced concrete (RC) bridge columns retrofitted with passive and active confinement systems. Four single-cantilever RC columns, representing 1/3-scale bridge piers, were constructed with poor transverse reinforcement detailing to simulate seismic deficiency. One column was left un-strengthened for baseline comparison, while the remaining three were retrofitted using: (1) a CFRP jacket, (2) welded Fe-SMA plates, and (3) bolted Fe-SMA plates. All columns were subjected to quasi-static lateral cyclic push-only loading reaching extreme drift levels exceeding 16% and high loading rates up to 6 mm/s. The study specifically explores the confinement effectiveness of CFRP and thermally activated Fe-SMA plates, comparing their contributions to lateral strength, ductility, energy dissipation, failure mode, and damage suppression. The results show that while the as-built column failed at 3.65% drift due to brittle flexural-shear failure, all retrofitted columns demonstrated significantly enhanced ductility, drift capacity, and post-peak behaviour. The CFRP and Fe-SMA jackets effectively delayed damage initiation, minimized core degradation, and improved energy dissipation. The bolted Fe-SMA system exhibited the highest and full restoration of lateral strength, while the welded system achieved the greatest increase in cumulative energy dissipation of around 40%. This research highlights the practical advantages and seismic effectiveness of Fe-SMA and CFRP confinement systems under extreme drift levels. However, future work should explore full-scale column applications, refine anchorage techniques for improved composite interaction, and investigate long-term durability under cyclic environmental conditions. Full article

This study proposes a hybrid flexural strengthening technique for reinforced concrete (RC) beams by combining the near-surface mounted (NSM) and externally bonded reinforcement (EBR) methods. In this technique, iron-based shape memory alloy (Fe-SMA) strips are used for the NSM component, while either a carbon fiber reinforced polymer (CFRP) sheet or an Fe-SMA sheet is applied as the EBR component. The proposed hybrid-strengthening method aims to enhance the flexural load capacity and ductility of existing RC beams. To evaluate the effectiveness of the proposed method, numerical models were developed using ABAQUS software and validated against experimental results. A comprehensive numerical investigation was carried out on 52 RC beams, categorized into six groups with various hybrid-strengthening configurations. In addition, the effect of the prestressing of NSM Fe-SMA strips and the prestressing of EBR CFRP or EBR Fe-SMA sheet on the flexural performance of the beams was also examined. The results indicated that the hybrid-strengthening method significantly improved the cracking, yielding, and ultimate load capacities of the beams; however, in most cases, it reduced their deflection. Notably, prestressing the EBR Fe-SMA sheet in beams with higher reinforcement ratios produced a pronounced improvement in ductility. Full article

Shape memory alloys (SMAs) are known for their exceptional mechanical properties, particularly their superior wear resistance compared to conventional alloys with similar surface hardness. Rare earth oxides are often used as additives to further improve these characteristics. This study investigates the effects of different CeO₂ (cerium dioxide) concentrations (0.01 wt.%, 0.1 wt.%, 0.5 wt.%, and 1.0 wt.%) on the properties of CuAlMnFe alloys produced via powder metallurgy (PM). Various analyses were performed, including scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray diffraction (XRD), as well as hardness, wear, and corrosion tests. The increase in wear rate is closely related to the formation of precipitates from CeO₂ addition. Improvements in wear resistance and hardness are attributed to the effects of grain refinement and solid solution strengthening due to CeO₂. Specifically, the wear rate increased from 1.5 × 10⁻³ mm³/(Nm) to 3.4 × 10⁻³ mm³/(Nm) with higher CeO₂ content. Additionally, the friction coefficient of the CuAlMnFe alloy was reduced with CeO₂ addition, indicating enhanced frictional properties. The optimal CeO₂ concentration of 0.5% was found to improve grain uniformity, resulting in better wear resistance. Incorporating CeO₂ particles into CuAlMnFe alloy enhances hardness and reduces wear rate when used in appropriate amounts. Additionally, it exhibits superior corrosion resistance, as evidenced by a positive shift in corrosion potential in Tafel measurements in solutions and a decrease in corrosion current density. The C0.5 specimen showed the highest corrosion potential (E_corr, −588 V) and the lowest corrosion current density (i_corr, 6.17 μA/cm²) during electrochemical corrosion in 3.5 wt.% NaCl solution. Full article

This study examines how the frequency of an innovative energy harvester is tuned and how it behaves. This harvester transforms thermal energy into mechanical oscillations of two polyvinylidene fluoride (PVDF) piezoelectric beams, which produce electrical energy via a shape memory alloy (SMA) thread. The oscillation frequency is modified by two magnetic weights that are positioned symmetrically on the SMA thread and interact with stationary NdFeB permanent magnets. The SMA thread shifts laterally due to longitudinal thermal contraction and expansion induced by a constant-temperature heater. Temperature gradients above the heater trigger cyclical variations in the length of the SMA thread, leading to autonomous vibrations of the masses in both the vertical and horizontal planes. An experimental apparatus was constructed to analyze the harvester by tracking the motions of the masses and the voltages produced by the piezoelectric beams. Information was gathered regarding the correlation between output voltage and power with the consumer’s load resistance. These outcomes were confirmed using a multiphysics dynamic simulation that incorporated the interconnections among mechanical, thermal, magnetic, and electrical systems. The findings indicate that the use of permanent magnets increases the bending vibration frequency from 8.3 Hz to 9.2 Hz. For a heater maintained at 70 °C, this boosts the output power from 1.9 µW to 8.18 µW. A notable property of the considered energy harvester configuration is its ability to operate at cryogenic temperatures. Full article

Reinforced concrete (RC) beams with openings in shear spans exhibited a significantly reduced structural performance due to disruptions in load transfer mechanisms. This numerical study investigated the influence of pre-stressed iron-based Shape Memory Alloy (Fe-SMA) rebars on the behavior of RC beams with web openings, focusing on the effect of shear-oriented design parameters, including the stirrup spacing, stirrup diameter, and horizontal reinforcement around the opening. A nonlinear finite element analysis (NLFEA) was conducted using ABAQUS/CAE software 2020 to simulate the response of RC beams under these conditions. The results showed that the presence of web openings in RC beams reduced the ultimate load capacity and stiffness. However, the pre-stressed Fe-SMA reinforcement effectively mitigated these adverse effects, restoring much of the solid beam’s performance. Among the studied parameters, reducing the stirrup spacing significantly improved the load-bearing capacity, with the smallest spacing (100 mm) restoring 86% of the solid beam’s ultimate load. Increasing the Fe-SMA stirrup diameter further enhanced performance, with T16 stirrups recovering 92% of the solid beam’s ultimate load capacity. The most substantial improvement occurred when horizontal reinforcement was introduced, particularly with T16 stirrups, achieving a 95% load recovery, nearly matching the solid RC beam structural performance. These findings demonstrated the promising potential of pre-stressed Fe-SMA reinforcement as a viable solution for restoring the structural strength of RC beams with web openings. Full article

The Monkeypox virus (MPXV), a DNA virus classified under the Orthpoxvirus genus alongside variola virus, has recently garnered significant global health attention due to its increasing transmission and emerging genomic mutations. Point-of-care testing is essential for effective clinical response and outbreak mitigation. In this article, we developed a novel class of colored microspheres designed for application in a lateral flow immunoassay (LFIA) platform targeting MPXV-specific biomarkers. Polystyrene-maleic anhydride (SMA-MAA) microspheres were synthesized with a high-temperature soap-free emulsion polymerization optimized in our lab. Subsequent alkali and acid treatments were employed to introduce porosity into the microsphere matrix. Solvent Red 27 and Disperse Red 60 were incorporated via solvent-swelling and thermal-swelling methods, respectively, to generate high brightness (HB) carriers. A surface coating composed of a tannic acid–iron (TA–Fe³⁺) coordination complex was applied to form a stable metal–polyphenol film (MPF). This coating not only minimized dye leaching by establishing a robust shell but also improved dye distribution, thereby enhancing overall color intensity. The final HB-LFIA system, configured in a sandwich immunoassay format, demonstrated favorable sensitivity and linear detection range for Monkeypox antigen, indicating strong potential for clinical diagnostic use. Full article