Search Results (54)

This study systematically investigates the effect of trace Ti addition on the impact toughness and underlying deformation mechanisms of high-Mn austenitic steel from 298 K to 4.2 K through instrumented Charpy impact testing, dynamic J-R curve analysis, and multi-scale microstructural characterization (SEM, TEM). The results show that Ti addition leads to the formation of Ti(C,N) precipitations, which act as microcrack initiation sites and significantly reduce the impact-absorbed energy at room temperature (298 K) from 249 J to 189 J. However, as the temperature decreases to liquid nitrogen (77 K) and liquid helium (4.2 K) temperatures, the impact toughness of the Ti-added steel does not deteriorate further and remains comparable to that of the Base steel. This temperature-dependent behavior originates from a transition in the dominant deformation mode. At room and moderately low temperatures, deformation is primarily governed by dislocation slip, whose strong interaction with coarse precipitates leads to premature cracking. At cryogenic temperatures, the significantly reduced stacking fault energy (SFE) shifts the deformation mechanism to the predominant formation of high-density nano-twins. These dense deformation twins enhance the matrix via the dynamic Hall–Petch effect and mitigate the detrimental effect of precipitates by alleviating interactions between dislocations and precipitates. Full article

Additive manufacturing of polymer materials, also known as 3D printing, is becoming a key technology for the production of functional parts with the ability to customize the structure and properties according to the application requirements. Polylactide (PLA) is one of the most commonly used materials in this field due to its biodegradability, ease of processing, and adequate strength for lightweight functional components. An important factor that affects the resulting properties of parts is not only the filler structure and density but also the angle at which the material is deposited during the printing process. This article focuses on investigating the influence of the printing angle (0°, 30°, 60° and 90°) and the bulk density of the filler (20%, 40%, 60% and 80%) on the mechanical properties of PLA samples. Two series of samples were prepared—the first was subjected to direct mechanical tests, and the second series was first exposed to freezing conditions and then tested to evaluate the effect of freezing on the material behavior. The samples were tested for tensile strength according to ASTM D638 and for bending strength according to ASTM D790. The results showed that the highest values were achieved in tensile strength in the 60°/80% configuration with a strength of 39.27 MPa, which represents more than a twofold improvement over the weakest configuration (0°/20%–19.58 MPa). In the bending test, the best results were achieved by the 90°/80% sample with a strength of 58.89 MPa, approximately 18% higher than 0°/20%. Cryogenic treatment caused a deterioration of all monitored parameters, especially at low infill densities and at an angle of 0°, where the decrease in strength reached up to 10–13%. These results confirm that the combination of a higher printing angle and a higher infill density is key to optimizing the mechanical properties of PLA parts, while cryogenic treatment has a negative impact on their behavior. Full article

Cryogenic industries handling liquid hydrogen and helium require rigorous safety verification. However, current standards (ASTM, ASME, ISO) are optimized for LNG at −163 °C and remain inadequate for extreme cryogenic conditions such as −253 °C. As the temperature decreases, materials experience ductile-to-brittle transition, raising the risk of sudden fracture in testing equipment. This study presents a fuzzy-integrated reliability framework that combines fault tree analysis (FTA) and Failure Modes, Effects, and Criticality Analysis (FMECA). The method converts qualitative expert judgments into quantitative risk indices for use in data-scarce conditions. When applied to a cryogenic impact testing apparatus, the framework produced a total failure probability of 1.52 × 10⁻³, about 7.5% lower than the deterministic FTA result (1.64 × 10⁻³). These results confirm the framework’s robustness and its potential use in cryogenic testing and hydrogen systems. Full article

Preimplantation genetic testing (PGT) reports play a decisive role in determining the fate of IVF-generated embryos. The identification of a chromosomal or genetic abnormality that could impact the health of the resulting newborn often leads to embryo disposal or indefinite storage in cryogenic containers. As a growing proportion of IVF cycles include PGT assessment, greater scrutiny is being placed on its clinical validity. Initially developed to detect monogenic disorders (PGT-M) and later expanded to identify full chromosomal aneuploidies, PGT is primarily used to identify embryos unlikely to implant (aneuploid), those that would lead to miscarriage, or those causing chromosomal syndromes or monogenic conditions. Advancements in genetic analysis now allow for the assessment of more complex traits and chromosomal features from a trophectoderm biopsy, including segmental aneuploidies, chromosomal mosaicism, and polygenic conditions. However, as technology pushes the limits of biological resolution, questions arise regarding the accuracy, clinical utility, and representativeness of these findings for the entire embryo. This article reviews the gold standards for validating clinical findings and reporting strategies, aiming to maximize diagnostic utility while minimizing false positives towards appropriately defined reproductive outcomes and phenotypes. Full article

The variable camber morphing wing has the potential to achieve improved flight performance across different flight conditions by changing its geometry according to changing flight conditions. Evaluating the subtle aerodynamic benefits of variable camber technology necessitates wind tunnel testing under flight Reynolds number conditions. In high Reynolds number wind tunnels, the cryogenic environment readily damages model surface profiles through desublimation and frost, compromising test data accuracy. Consequently, cryogenic wind tunnels must enforce rigorous water vapor control standards. To address potential water vapor effects during cryogenic wind tunnel testing, high-resolution optical measurement techniques were employed to quantify the spatiotemporal evolution of desublimation frost thickness on a typical supercritical airfoil surface. Combined with numerical simulations, the mechanisms governing the frost layer’s influence on aerodynamic characteristics and flow field structures were systematically investigated. The results reveal that the influence of water vapor desublimation on the aerodynamic characteristics under diverse cryogenic working conditions has a commonality, and the difference in aerodynamic parameters shows an increasing tendency as the frost time increases; water vapor desublimation has an obvious influence on the flow structure of the airfoil and its pressure distribution on the surface, which increases flow instability and leads to the backward shift of the shock wave position; larger frost thickness gradients along the flow direction cause more drastic changes in pressure distribution and flow structure; and a larger rate of water vapor desublimation results from a lower temperature and a higher concentration of water vapor in the test environment, which causes frosting to have a more severe impact on the airfoil’s aerodynamic characteristics and flow structure. The findings establish a technical basis for cryogenic wind tunnel moisture control standards and provide a solid foundation for the refined assessment of aerodynamic benefits of the camber morphing wing. Full article

The anisotropic mechanical properties of selective laser melting (SLM)-processed Ti-6Al-4V (TC4) alloy hinder its deployment in polar marine equipment. This study systematically probes the relationships between laser scanning strategies (unidirectional vs. 67°-rotated scanning between layers), notch orientation (governing loading direction), and cryogenic impact energy of SLM-TC4. Charpy impact tests from −60 °C to 20 °C were performed on V-notched specimens fabricated with distinct scanning strategies and notch orientations (top/side surfaces). The analysis of impact energy data and macro/micro-fractography demonstrates that impact energy declines markedly with decreasing temperature, showing a 25–35% reduction at −60 °C versus 20 °C while exhibiting enhanced data consistency under cryogenic conditions. Notably, specimens fabricated with 67°-rotated scanning between layers achieve higher impact toughness than unidirectionally scanned equivalents. Moreover, for identical scanning strategies, side-notched specimens consistently outperform top-notched specimens, evidencing superior interfacial bonding strength between deposited layers relative to bonding within individual layers. Within individual layers, toughness normal to the laser scan path exceeds that parallel to the path. However, controlling ductile-to-brittle transition behavior and precluding brittle failure are imperative for SLM-TC4 components in polar cryogenic service. This work delivers essential quantitative benchmarks and experimental validation for optimizing SLM processing in critical polar vessel components. Full article

Patient-tailored, 3D-printed surgical guides offer significant potential to improve precision and therapeutic efficacy in cardiac ablation surgery. However, reliable post-sterilization material performance presents a critical yet underexplored barrier to clinical adoption. This study investigates how disinfection and sterilization impact the mechanical and thermal properties of photopolymer resins. Specimens from two 3D-printing resins (Bioflex A80 MB™, 3Dresyns; MED625FLX™, Stratasys) were treated with four combinations of disinfection techniques (low-temperature manual cleaning; high-temperature machine washing) and sterilization techniques (H₂O₂ vs. autoclaving). We assessed post-sterilization properties by mechanical (material integrity, bending tests), thermal (differential scanning calorimetry, thermogravimetric analysis), and viscoelastic (dynamic mechanical analysis) studies. Statistical analysis was performed using one-way ANOVA with Bonferroni post hoc tests (α = 0.05). From this preliminary study, we conclude that MED625FLX maintains integrity and flexibility across all tested disinfection and sterilization methods. Bioflex A80 MB is only suitable for low-temperature disinfection–sterilization, as high-temperature treatments cause surface cracking. Neither resin is appropriate for cryogenic conditions due to the risk of brittleness. Further research into post-sterilization properties is essential to ensure the safety and clinical reliability of these materials in cardiac procedures. Full article

Different polyurethanes (PURs) and silicone for potential use in particle accelerators and detectors have been characterized in the uncured state, after curing, and after exposure to ionizing irradiation in ambient air and in liquid helium. The viscosity evolution during processing was measured with a rheometer. Dynamic mechanical analysis (DMA) and Shore A hardness measurements were applied to detect irradiation-induced crosslinking and chain scission effects. Uniaxial tensile and flexural tests under ambient and cryogenic conditions have been performed to assess changes in mechanical strength, elongation at break, and elastic properties. The initial viscosity of 550 cP at 25 °C of the uncured PUR RE700-4 polyol and RE106 isocyanate system for protective encapsulation is sufficiently low for impregnation of small magnet coils, but the pot life of about 30 min is too short for impregnation of large magnet coils. The cured RE700-4 system has outstanding mechanical properties at 77 K (flexural strength, impact strength, and fracture toughness). When RE700-4 is exposed to ionizing radiation, chain scission and cross-linking occur at a similar rate. In the other casting systems, irradiation-induced changes are cross-linking dominated, as manifested by an increase of the rubbery shear modulus (G’_rubbery), the ambient temperature Young’s modulus (E_RT), and the Shore A hardness. Cross-linking rates are strongly reduced when irradiation occurs in liquid helium. The irradiation effect on mechanical properties can be strongly dependent on the testing temperature. The RT mechanical strength and strain at fracture of the cross-linking silicone is drastically decreased after 1.6 MGy, whereas its 77 K strain at fracture has almost doubled. In addition, 77 K elastic moduli are similar for all pure resins and only slightly affected by irradiation. Full article

The long-term reliability of vacuum insulation panels (VIPs) is constrained by the barrier film degradation caused by micro-cracks during the flanging process. However, the correlation mechanism between process parameters and microleakage remains unclear. This study systematically investigates the impact of the number of flanging cycles on the barrier properties and insulation failure of aluminum foil composite film (AF) and metallized polyester film (MF). Accelerated aging tests revealed that the water vapor transmission rate (WVTR) of MF surged by 340% after five flanging cycles, while its oxygen transmission rate (OTR) increased by 22%. In contrast, AF exhibited significantly increased gas permeability due to brittle fracture of its aluminum layer. Thermal conductivity measurements demonstrated that VIPs subjected to ≥5 flanging cycles experienced a thermal conductivity increase of 5.22 mW/(m·K) after 30 days of aging, representing a 7.1-fold rise compared to unbent samples. MF primarily failed through interfacial delamination, whereas AF failed predominantly via aluminum layer fracture. This divergence stems from the substantial difference in mechanical properties between the metal and the polymer substrate. The study proposes optimizing the flanging process (≤3 bending cycles) and establishes a micro-crack propagation prediction model using X-ray computed tomography (CT). These findings provide crucial theoretical and technical foundations for enhancing VIP manufacturing precision and extending service life, holding significant practical value for energy-saving applications in construction and cryogenic fields. Full article

This study systematically evaluates the influence of copper (Cu) addition in gas-shielded solid wires on the microstructure and cryogenic toughness of X80 pipeline steel welds. Welds were fabricated using solid wires with varying Cu contents (0.13–0.34 wt.%) under identical gas metal arc welding (GMAW) parameters. The mechanical capacities were assessed via tensile testing, Charpy V-notch impact tests at −20 °C and Vickers hardness measurements. Microstructural evolution was characterized through optical microscopy (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Key findings reveal that increasing the Cu content from 0.13 wt.% to 0.34 wt.% reduces the volume percentage of acicular ferrite (AF) in the weld metal by approximately 20%, accompanied by a significant decline in cryogenic toughness, with the average impact energy decreasing from 221.08 J to 151.59 J. Mechanistic analysis demonstrates that the trace increase in the Cu element. The phase transition temperature and inclusions is not significant but can refine the prior austenite grain size of the weld, so that the total surface area of the grain boundary increases, and the surface area of the inclusions within the grain is relatively small, resulting in the nucleation of acicular ferrite within the grain being weak. This microstructural transition lowers the critical crack size and diminishes the density for high-angle grain boundaries (HAGBs > 45°), which weakens crack deflection capability. Consequently, the crack propagation angle decreases from 54.73° to 45°, substantially reducing the energy required for stable crack growth and deteriorating low-temperature toughness. Full article

This study aims to comprehensively assess the suitability of post-processing annealing (at 900–1200 °C) for enhancing the key properties of 316L steel fabricated via laser powder bed fusion (LPBF). It adopts a holistic approach to investigate the annealing-driven evolution of microstructure–property relationships, focusing on tensile properties, nanoindentation hardness and modulus, impact toughness at ambient and cryogenic temperatures (−196 °C), and the corrosion resistance of LPBF 316L. Annealing at 900–1050 °C reduced tensile strength and hardness, followed by a moderate increase at 1200 °C. Conversely, ductility and impact toughness peaked at 900 °C but declined with the increasing annealing temperature. Regardless of the annealing temperature and testing conditions, LPBF 316L steel fractured through a mixed transgranular/intergranular mechanism involving dimple formation. The corrosion resistance of annealed steel was significantly lower than that in the as-built state, with the least detrimental effect being observed at 1050 °C. These changes resulted from the complex interplay of annealing-induced structural transformations, including elimination of the cellular structure and Cr/Mo segregations, reduced dislocation density, the formation of recrystallized grains, and the precipitation of nano-sized (MnCrSiAl)O₃ inclusions. At 1200 °C, an abundant oxide formation strengthened the steel; however, particle coarsening, combined with the transition of (MnCrSiAl)O₃ into Mo-rich oxide, further degraded the passive film, leading to a sharp decrease in corrosion resistance. Overall, post-processing annealing at 900–1200 °C did not comprehensively improve the combination of LPBF 316L steel properties, suggesting that the as-built microstructure offers a favorable balance of properties. High-temperature annealing can enhance a particular property while potentially compromising other performance characteristics. Full article

The Charpy impact toughness of single-phase austenitic Fe-32Mn-0.6C steel was systematically investigated across a wide temperature spectrum from 25 °C to −196 °C using Charpy V-notch impact tests. The material exhibited a remarkable temperature dependence of impact energy, decreasing dramatically from 120 J at ambient temperature (25 °C) to 13 J under cryogenic conditions (−196 °C). Notably, a steep transition in impact energy occurred within the critical temperature window of −100 °C to −150 °C. Microstructural analysis revealed that synergistic effects of high strain rates and low temperatures significantly restrict dislocation slip and multiplication mechanisms, while also suppressing deformation twinning activation. This restricted plasticity accommodation mechanism fundamentally differs from the deformation characteristics reported in conventional low-carbon high-manganese steels and other face-centered cubic (FCC) alloy systems. Full article

Interest in hydrogen is rapidly growing due to rising greenhouse gas emissions and the depletion of fossil fuel reserves. Additive manufacturing (AM) is extensively employed to produce high-quality components, with a strong focus on enhancing mechanical properties. The efficiency and cost-effectiveness of AM have further increased interest in its application to manufacturing components capable of withstanding demanding conditions, such as those encountered in hydrogen technology. In this study, 316L stainless steel specimens were fabricated using AM via the selective laser melting (SLM) technique. The specimens then underwent various post-processing heat treatments (PPHT). A subset of these specimens, measuring 50 × 50 × 3 mm³, was tested as electrodes in a water electrolysis cell for oxyhydrogen (HHO) gas production. The HHO gas flow rate and electrolyzer efficiency were evaluated at 60 °C under varying currents. The remaining AM specimens were evaluated for their susceptibility to hydrogen embrittlement under various hydrogen storage conditions, including testing at both room and cryogenic temperatures. Tensile and Charpy impact specimens were fabricated and tested before and after hydrogen charging. The fracture surfaces were analyzed using scanning electron microscopy (SEM) to assess the influence of hydrogen on fracture characteristics. Additionally, as-rolled stainless-steel specimens were examined for comparison with AM and PPHT 316L stainless steel. The primary objective of this study is to determine the most efficient alloy processing condition for optimal performance in each application. Results indicate that PPHT 316L stainless steel exhibits superior performance both as electrodes for HHO gas production and as a material for hydrogen storage vessels, demonstrating high resistance to hydrogen embrittlement. Full article

This study examines the mechanical behavior and deformation mechanisms of hot-forged 304L stainless steel for cryogenic applications such as LNG storage and low-temperature structural systems. Tensile testing revealed a significant strength increase from 618 MPa at room temperature to 1432 MPa at cryogenic temperatures, with elongation decreasing from 83.7% to 23.3%. Charpy impact testing showed a 28% reduction in absorbed energy at cryogenic temperatures due to enhanced strain-induced martensitic transformation (SIMT). The observed mechanical responses are attributed to reduced stacking fault energy (SFE) at lower temperatures, which promotes SIMT, deformation twinning, and dislocation interactions, affecting material strength and toughness. SEM and EBSD analysis confirmed extensive martensitic transformation, increased deformation twinning, and reduced remaining austenite, indicating a γ → ε → α’ transformation pathway that governs strain hardening. The high strain rate during Charpy impact testing induced localized adiabatic heating, partially suppressing SIMT and modifying fracture behavior by enhancing localized plasticity. These findings emphasize the interplay between SFE, strain rate, and phase transformation in governing the cryogenic mechanical performance of 304L stainless steel. Full article

STS304L is widely used in liquefied natural gas cargo containment systems for cryogenic liquefied gas storage because of its excellent mechanical properties at low temperatures. However, unpredictable sloshing impacts can induce excessive plastic deformation, leading to phase transformation from austenite to martensite. This study investigated the impact resistance of STS304L under cryogenic conditions through drop-weight impact tests. Temperature sensitivity was analyzed using electron backscatter diffraction to quantify plastic deformation and phase fraction. The results showed that, as the temperature decreased, the energy absorption and stiffness increased, whereas the plastic deformation remained relatively constant. Energy absorption increased by 59.63% at −100 °C and 68.80% at −193 °C compared with that at 20 °C. The martensite fraction, measured at the end of the hemispherical impact region, increased from 19.26% at 20 °C to 77.85% at −100 °C and 96.87% at −193 °C, indicating significant strain-induced martensitic transformation at cryogenic temperatures. Full article