Constructing an effective and scalable anti-counterfeiting system against cyber-physical attacks has become an increasingly crucial problem. While mass production and digitalization across many domains profoundly transformed our society with an abundance of goods and hyper-connectivity, they have also made it harder to track products and associated information, thereby raising authentication risks. In response to such risks, leveraging random physical traces that are generated as byproducts in manufacturing processes has gained great attention as a robust and efficient replacement for existing approaches. Yet, as current methods of generating such inherently unique patterns rely on complex process setups and specific materials, they face significant limitations to be applied and scaled up as a product authentication system in various manufacturing industries. To address this issue, we propose a Physically Unclonable Identifier (PUID) that exploits the inherent randomness and process characteristics of Pulsed Cold Spray (PCS) to fabricate a unique physical identifier. In addition, we develop a complementary framework that leverages the resulting spectral features for reliable product identification. Specifically, our framework utilizes Implicit Neural Representations (INRs) and Fast Fourier Transform (FFT)-based cross-correlation as key strategies to create, register, manage, and authenticate PUIDs. Through experiments, we validate the robustness, applicability, and scalability of our approach by rapidly generating 54 PUIDs on an arbitrary substrate and successfully authenticating each one. These results highlight the significant potential of PUIDs for deployment across various industries.

This study investigated the ultrasonic fatigue behavior of ABS and of a high-strength photopolymer resin (Rigid Black) fabricated by digital light processing (DLP) additive manufacturing. The dynamic elastic modulus of both materials was measured so that specimens could be designed to satisfy the 20 kHz resonance condition. ABS specimens were CNC-machined, whereas Rigid Black specimens were DLP-printed and post-cured. Thermal effects were minimized by compressed-air cooling with a 0.3 s/3 s duty cycle. S-N curves showed that fatigue life increased as the stress amplitude decreased for both materials. ABS exhibited higher fatigue strength and a more consistent life distribution, which is attributed to its homogeneous microstructure. Rigid Black showed lower fatigue strength with greater scatter, reflecting the anisotropy and interfacial inhomogeneity introduced by layer-by-layer fabrication. Fractographic analysis revealed that ABS underwent mixed-mode ductile-fatigue fracture through crazing, whereas Rigid Black failed in a brittle manner, with directional crack propagation driven by process-induced defects. These results confirm the feasibility of ultrasonic fatigue evaluation for DLP-printed polymer components and provide a basis for assessing the durability of additively manufactured parts.

This study examines the low-temperature, high-stress creep behavior of a niobium-based alloy, Nb-1 wt% Zr (NbZr1), produced by wire-arc additive manufacturing (WAAM), in comparison with its powder metallurgy (PM) counterpart. Creep tests conducted at 300 degrees C showed that deformation in both materials was largely governed by the primary creep stage. WAAM specimens failed at 150 MPa, whereas PM specimens endured up to 250 MPa, demonstrating its superior creep strength. WAAM specimens exhibited greater strain accumulation (similar to 3.5 % at 150 MPa) and stronger stress sensitivity. Fractographic analysis revealed that WAAM specimens fractured primarily along interdendritic regions, while PM alloy failed due to void formation at grain boundaries and triple points. To capture strain evolution during primary creep, empirical fits based on logarithmic and power-law functions were applied, with the logarithmic model providing the best fit. These findings demonstrate that WAAM-induced microstructural features degrade creep resistance relative to PM processing and offer an empirical framework for describing primary creep strain evolution in Nb-Zr alloys under low-temperature, high-stress conditions.

This study investigates the effects of three heat treatment conditions-stress relief, recrystallization annealing, and solution treatment with aging-on the microstructure, tensile properties, and high-cycle fatigue (HCF) behavior of wire-arc additively manufactured 90WNiFe-Inconel 625 bimetallic structures. After heat treatment grain coarsening was observed in Inconel 625 (95-200 mu m) side, while 90WNiFe grains experienced slight reduction in size (12-17 mu m). Stress relief and recrystallization annealing promoted delta-Ni3Nb, modified Laves phases, and carbide precipitates at the interface, whereas delta-Ni3Nb was dissolved after solution treatment with aging. The as-built solidification texture of WAAM-Inconel 625 was mostly preserved, with grain growth partially disrupting the strong < 001 > texture following solution treatment and aging. The highest tensile strength was achieved for stress relief condition (758 MPa, 14 % above as-built), while solution treatment with aging provided the highest ductility (35 % elongation, 28 % increase). High cycle fatigue testing (R = 0.1) after stress relief demonstrated extended fatigue life from 10(6) to beyond 10(8) cycles, with most specimens surviving >20 million cycles at 150 MPa. Improvements in fatigue performance were attributed to increased ductility and reduced residual stress, as no interfacial failures were observed below 90 % yield strength. Fracture occurred in bulk Inconel 625 or 90WNiFe regions, with crack initiation dominated by surface defects. Fractography revealed mixed ductile-brittle failure in Inconel 625 and brittle fracture in 90WNiFe while crack propagation was influenced by the presence of secondary delta-Ni3Nb particles.

The bimetallic structure of stainless steel 316 L (SS316L) and Inconel 625 (In625) offers an excellent combination of strength, corrosion resistance, and thermal stability, making it a promising candidate for high-temperature applications. This study investigates, for the first time, an integrated experimental and computational approach to predict the mechanical behavior of wire-arc directed energy deposited SS316L-In625 bimetallic structures. Electron backscatter diffraction (EBSD) analysis indicates large columnar grains (average 453 & micro;m and 568 & micro;m for SS316L and In625, respectively) and prominent directional texture in the microstructure. These grain statistics are utilized to generate a representative volume element (RVE) of SS316L and In625. These are combined, and the Potts model is implemented to generate the bimetallic RVE. A phenomenological crystal plasticity (CP) model has been implemented and solved utilizing a fast Fourier transform (FFT)-based approach by applying appropriate boundary conditions. The constitutive parameters of the CP model are optimized using a Bayesian optimization framework. The predicted yield strength (362 MPa) and ultimate tensile strength (800 MPa) differ approximately 2% from the experimental values, demonstrating excellent agreement. Digital image correlation (DIC) indicates that strain localizes predominantly on the SS316L side of the bimetallic specimen. The simulation accurately captures the strain localization observed in the DIC analysis. It further demonstrates local stress heterogeneity throughout the SS316L and In625 side of bimetallic RVE, which can be attributed to the presence of large grain size and strong texture. The proposed approach effectively captures the influence of microstructural heterogeneity on the mechanical behavior of bimetallic structures.

This study presents an integrated experimental and computational approach to predict the mechanical properties of wire-arc directed energy deposited (DED) aluminum 4043 (Al4043) structure. Thermo-metallurgical simulation has been performed to identify a deposition strategy that reduces heat accumulation during the deposition process. Based on the simulation results, a raster deposition strategy and a lower interpass temperature (50 degrees C) have been maintained during the fabrication to minimize temperature buildup and promote microstructural homogeneity. Electron backscatter diffraction (EBSD) analysis and mechanical testing with digital image correlation reveal the presence of isotropic mechanical properties (difference is less than 4% across three independently tested samples per direction). Porosity, commonly present in the wire-arc DED Al4043 structures, has been quantified using X-ray micro-computed tomography (X-CT). Representative volume elements (RVEs) are generated utilizing EBSD data from two perpendicular planes and pore size distribution from X-CT. The phenomenological crystal plasticity (CP) framework has been utilized to simulate deformation behavior and study local stress-strain behavior considering the effect of grain statistics and porosity. The CP model parameters are calibrated and validated utilizing an iterative Bayesian optimization framework by matching simulated stress-strain curves with tensile test data along the build direction and deposition direction, respectively. Calibration result indicates discrepancy of 1.4 f 0.15% for yield strength and 1.1 f 0.12% for ultimate tensile strength, whereas model validation shows discrepancies of 2.9 f 0.2% and 1.5 f 0.2%, respectively, for the corresponding values. The CP simulations reveal a high level of consistency in the local stress-strain response across the RVEs, further supporting the presence of a homogenous structure.

This study investigates the corrosion behavior and mechanical performance of multi-material structures composed of W7Ni3Fe tungsten alloy and 316L stainless steel (SS316L) with an Inconel 625 (IN625) interlayer, designed for application in corrosive environments. The structure was fabricated using wire-arc directed energy deposition (DED) followed by heat treatment at 900 °C for 2 hours with furnace cooling. ReaxFF Molecular Dynamics (MD) was considered to study the mechanism of interface corrosion in 3.5 wt.% NaCl solution for a duration of 500, 1000, and 1500 hours. Long-term immersion tests in 3.5 wt.% NaCl solution revealed a decreasing corrosion rate—from 9.34 × 10⁻³ mm/year after 500 hours to 6.77 × 10⁻³ mm/year after 1500 hours—indicating progressive surface passivation. Surface analysis identified WO₂, Fe₃O₄, and Cr₂O₃ as dominant corrosion products. Electrochemical tests showed that IN625 interlayer exhibited the most noble behavior (Ecorr = −223 mV, Icorr = 1.4 µA/cm²), followed by SS316L and W7Ni3Fe. The overall corrosion rate estimated from Icorr was 18.8 × 10⁻³ mm/year, moderately matching the mass-loss-based corrosion rates. The MD simulations confirmed the experimental surface analysis and indicated that an increasing number of oxygens, OH, and chloride ions accumulate at the surface and participate in the corrosion process as the simulation progresses. Mechanical testing indicated that the ultimate tensile strength decreased by 7.3%, from 602 ± 7 MPa before immersion to 558 ± 8 MPa after 1500 hours of immersion, confirming that the structure retained most of its mechanical integrity despite localized corrosion, particularly in the W7Ni3Fe region.

Large colonic perforations rarely occur during endoscopic diagnosis and treatment; however, when they do occur, they may require additional surgery and may lead to medical disputes, posing challenges for physicians and increasing the burden on patients. If a perforation can be closed endoscopically with clips, these burdens and conflicts may be reduced. However, owing to the geometric limitations of conventional clips, perforations exceeding a certain size are difficult to manage. In large perforations, the distance between the opposing tissue edges is often too great to allow closure with conventional clips. In this study, we propose a method in which a permanent magnet is added to a conventional endoscopic clip. The magnetic force generated between two such clips draw the opposing edges of the perforation closer together, thereby reducing the gap between them. Once the distance is sufficiently reduced, the perforation can be closed using conventional clips. The device can be inserted through the working channel of an endoscope and can exert a magnetic traction force of at least 0.8 N on the surrounding tissue. To increase the traction force, a magnetic configuration incorporating a yoke and magnet was designed based on a finite element magnetic field analysis. To evaluate the effectiveness of the device, gastroenterologists conducted experiments using an in vitro swine colon model. The results confirmed that large perforations exceeding 15 mm in diameter can be narrowed by magnetic traction. After traction, conventional endoscopic clips were used for suturing. This device should improve procedural convenience for physicians and facilitate patient recovery by enabling the endoscopic management of large perforations during diagnostic and therapeutic procedures.

A coupled thermo-mechanical finite element framework was developed to analyze the influence of heat treatment on the thermal history, phase evolution, and mechanical responses of Inconel 625 walls fabricated by wire arc additive manufacturing (WAAM). The model captures transient heat transfer, molten pool behavior, phase transformations, and the resulting residual stress and distortion fields. Mesh sensitivity analysis was performed to ensure numerical stability and computational efficiency. The simulations demonstrate that heat treatment promotes a more homogeneous phase distribution and stabilizes the arc process, resulting in a more uniform residual stress profile. Temperature fields increase nonlinearly with build height, and the stress state transitions from tensile near the substrate to compressive in upper layers. Distortion is more sensitive to heat treatment than residual stress, with notable reductions observed in thin-wall geometries. A multi-material configuration combining stainless steel and Inconel 625 was also modeled, revealing sharp interfacial transitions and characteristic morphological features consistent with experimental observations. Overall, the results provide mechanistic insight into heat-treatment-driven improvements in structural integrity, offering guidance for optimizing WAAM process parameters for both single- and multi-material builds.

Multilayer depositions with varying interface behaviors affect the mechanical properties of deposited materials, so atomic-scale deposition mechanisms provide a better understanding of material behavior under multiple diffusion conditions. In this research, molecular dynamics is applied to investigate the behavior of the interface in Ti6Al4V-NbZr1 bimetallic structure deposited by wire-arc directed energy deposition (W-DED) in various heat input conditions. In addition, the interactions between the bimetallic structure and the distribution and size of dislocation loops are studied during deformation. It was found that the nano-melting pool forms before solidification, and the crystal growth proceeds by directional solidification, which can be equiaxed or columnar. Interdiffusion of the system shows asymmetrical diffusion behavior, and Nb atoms show a greater tendency to diffuse into the matrix in higher heat input conditions. According to the cluster analysis, the cluster number decreases from 76,138 to 75,720 for the first deposited layer, whereas it increases from 88,046 to 90,309 for the final deposited layer as heat input increases. Surface roughness decreases from 1.6 to 0.9 & Aring; while the interface width increases from 30 to 50 & Aring; as the heat input increases. It was concluded that atomic-size mismatch-induced lattice distortion enhances residual stress, resulting in dislocation loops. The formation of numerous 1/6 (112) Shockley and 1/2 (111) interstitial dislocation loops, along with a low amount of (100) and mixed loops, was also observed. At the substrate-interface, the biaxial stress is compressive, whereas the deposited layers exhibit tensile behavior.

Background: This study explores effective fixation methods for Pauwel type III femoral neck fractures by evaluating the biomechanical benefits of adding a screw to the Femoral Neck System (FNS). Methods: Computed tomography (CT) scans of an 82-year-old female patient with an intertrochanteric fracture were used to establish a finite element femur model with heterogeneous material properties. Finite element models of Pauwel type III fractures were created with and without an additional screw. The central and inferior trajectories of the FNS bolt were examined separately and combined with an additional screw for virtual fixation. Walking and stair-climbing loads were applied. Results: With the addition of a screw, both peak maximum and minimum principal strains consistently stayed comparable or decreased in models with both central and inferior bolt trajectories, while the volume of elements with principal strain exceeding 1% decreased by more than half. The peak von Mises stress observed in the implants ranged from 215.7 to 359.3 MPa, remaining below the titanium alloy's yield strength of 800 MPa. For normal walking, the addition of a screw to the central bolt trajectory model decreased the fracture gap by 50.6% and reduced sliding distance by 8.6%. For the inferior bolt trajectory, the gap was reduced by 57.9% and sliding distance by 25.0%. Under stair-climbing conditions, these improvements were also evident; the central trajectory model saw a halved fracture gap and a 7.9% decrease in sliding distance, while the inferior trajectory model experienced a 55.7% gap reduction and a 27.2% decrease in sliding distance. The additional screw increased the area ratio of the fracture site experiencing interfragmentary compression 34%-39%, while the additional screw alleviated peak interfragmentary compression by 12%-18% under both normal walking and stair-climbing conditions. Conclusions: The addition of a screw reduced the fracture gap, sliding distance, and peak interfragmentary compression, while increasing the area ratio of interfragmentary compression under both walking and stair-climbing loads, regardless of the FNS bolt trajectory, suggesting a better mechanical environment for fracture healing.

Functionally graded metallic materials (FGMMs) represent an innovative category of metals, characterized by gradual variations in structure or composition, achieved by combining different elements. FGMMs differ from traditional materials as they enable the combination of diverse properties in a spatially tailored manner, offering extraordinary combinations of advanced functionalities. The unique capabilities of FGMMs make them highly desirable for various applications across different industries. The initiation of additive manufacturing (AM) has significantly progressed the advance of FGMMs by aiding specific control over material gradients, complex geometries, and optimized material utilization. This review delivers a comprehensive overview of FGMMs, including their fundamental principles, metallic alloys (alloys based on Al, Ti, Fe, superalloys, and emerging high-entropy alloys), and their integration with AM technologies. Challenges related to thermophysical mismatches, thermal stresses, and process monitoring are addressed with potential solutions. Further, Key modeling and simulation approaches, such as thermodynamic modeling, thermal-mechanical simulations, and machine learning-based design, are discussed in detail to highlight their role in optimizing FGMM performance. This review provides an in-depth exploration of recent advancements in FGMMs, highlighting their classifications, modeling and computational approaches, applications, challenges, and future prospects. The article includes a detailed analysis of the microstructure, texture, mechanical properties, and their applications in various sectors. It aims to benefit both general readers seeking an understanding of FGMMs and researchers dedicated to advancing this transformative field.

Integrating materials with distinct properties (e.g., tungsten and steel) into a single structure offers significant performance benefits for demanding engineering applications. Among available manufacturing techniques, wire-arc directed energy deposition (DED) has gained attention for its capability to fabricate complex multi-material components with minimal waste. Nevertheless, the integration of tungsten and steel remains challenging due to their mismatched thermal and mechanical characteristics, which often result in high residual stresses and weak interfacial bonding. In this study, heat treatment was investigated to improve the structural integrity of wire-arc DED-fabricated tungsten/steel components. Instead of relying solely on experimental trial-and-error, simulations were employed to determine a suitable heat treatment condition-holding at 900 degrees C for 120 min followed by cooling at 5 degrees C/min. This treatment effectively relieved residual stress while simultaneously altering the microstructure: the tungsten alloy exhibited grain refinement, whereas the steel showed moderate grain coarsening. Mechanical testing demonstrated a 16 % increase in tensile strength, from 521 +/- 4 MPa in the as-printed condition to 602 +/- 7 MPa after heat treatment. Notably, the fracture location shifted from interface in the as-printed state to within the steel region after heat treatment, confirming enhanced interfacial bonding.

Pulsed cold spray (PCS) is a type of cold spray metal coating technique that incorporates cyclical compressed gas pulses to control the gas-powder for improved surface deposition. In recent years, PCS has garnered great attention owing to its unique pulsed nature in the domains of dense coatings, metal matrix composite coatings, cellular metallic structures, etc. However, research on the PCS to uncover process-structure-property relationships of this emerging deposition technique is limited. To this end, this study thoroughly investigates PCS to gain a deeper understanding of this coating technique. First, a PCS system incorporating a converging-diverging (CD) nozzle is designed and prototyped. Next, two-phase flow (i.e., gas + powder) within the PCS is modeled using computational fluid dynamics (CFD). The modeling results are then experimentally validated using particle image velocimetry (PIV), followed by a case study on surface deposition. The results show that the optimal powder injection window occurs when the gas inlet pressure is at least 99 % of the set inlet pressure, achieving a steady-state gas flow for 100 ms. CFD modeling showed that Mach diamonds formed at the nozzle exit by 30 ms, though powder velocity does not reach steady-state until 50 ms. Numerical modeling captured the average particle with an error of approximate to 8 % as compared to the PIV measurements. Furthermore, surface deposition experiments showed that the PCS can create dense coatings with remarkably less porosity (i.e., 1.73-fold) as compared to the traditional CS. Overall, this study unravels the intricacies of designing and modeling of a PCS system with a CD nozzle, complemented by surface deposition experiments.

Understanding atomic-scale evolution is critical to tailoring the mechanical behavior of bimetallic materials in additive manufacturing. In this study, we apply molecular dynamics (MD) simulation to investigate the microstructural and mechanical evolution of Ti6Al4V/NbZr1 bimetallic structures fabricated using wire arc additive manufacturing (WAAM) under low, medium, and high heat input conditions: 180 A (LHI), 200 A (MHI), and 220 A (HHI), respectively. An eight-layer deposition model was simulated to analyze phase transformation, grain growth, dislocation behavior, and interface diffusion. Results indicate that higher heat inputs promote greater atomic mobility and interfacial mixing, leading to increased cluster formation and amorphization, while lower heat inputs yield finer grains and higher tensile strength. Transverse tensile specimens consistently showed higher strength than longitudinal ones, attributed to directional microstructural effects. This work provides atomic-level insights into the relationship between thermal input and microstructure-property correlations in WAAM-fabricated bimetallic systems.

Refractory alloys (RAs) are promising materials due to their exceptional physicochemical properties, but most research remains at the laboratory scale. For broader adoption, advancements in manufacturing are essential. Because their high stability makes conventional methods like machining and casting difficult, additive manufacturing (AM) is emerging as an effective approach for fabricating refractory alloy components. However, AM's repeated non-equilibrium thermal cycles introduce undesired features (e.g. defects, anisotropic microstructures, and residual stresses), which are magnified due to RAs’ unique properties. This paper comprehensively reviews the state-of-the-art methods of AM for refractory alloys. It explores data analytics techniques to establish design rules based on multi-fidelity experimental and computational methods. Furthermore, it investigates integrated, collaborative efforts to harmonise standalone databases, information, knowledge, and predictive models at multi-physics, multi-stage, and multi-scale. Unlike the existing literature that focuses primarily on material systems or process fundamentals, this work provides an integrated perspective on AM of refractory alloys from a data analytics standpoint, highlighting the roles of integrated computational materials engineering (ICME), verification, validation, and uncertainty quantification (VV&UQ), and digital twin-driven qualification in overcoming data scarcity and accelerating rapid qualification.

Backgroud:The removal of a well-fixed acetabular cup is a challenging, labor-intensive, and time-consuming step during revision hip arthroplasty. Although the advent of the manual osteotome, Explant, has simplified the procedure, it is still a stressful process as it dissipates the surgeon's strength and time and risks an iatrogenic pelvic fracture. Recently, EZX, a powered tool for extraction of well-fixed acetabular cups with semicircular blade was invented. This study aimed to compare Explant and EZX in an experimental condition for their efficacy and safety. Methods:Cementless acetabular cups were press-fitted to 20 hemipelvic polyurethane models using foam adhesives. Ten cups were removed with each tool for comparison of the elapsed time, loads on the entire hemipelvis, periacetabular strain and temperature, volume of periacetabular bone removed, and diameter of the remaining acetabular rim. Strains and loads were quantitatively assessed using strain gauges and load cells for precise and reliable measurements. Results:The mean duration required to remove a well-fixed cup with EZX was 38.5 seconds (range, 25-55), whereas that with Explant was 543.7 seconds (range, 214-1,051) (p < 0.001). The load on the entire hemipelvis with EZX (mean, 9.1 kgf; range, 6.4-11.3) was 33% lower than that with Explant (mean, 13.6 kgf; range, 9.2-17.1) (p < 0.001). The periacetabular peak strains at the 3 positions with EZX were significantly lower than those with Explant (p < 0.001). The temperature during the removal did not differ significantly between the 2 tools. Although the mean volume of bone loss with Explant was 2.4 mL more than that with EZX (p < 0.001), the mean diameters of the remaining acetabular rim were not significantly different, measuring 54.1 mm with both tools. Conclusions:The present experiment revealed that a well-fixed cup could be removed using a powered tool with less strength and time and less load on the entire pelvis. Although the powered tool removed a larger volume of bone, the diameters of the remaining acetabular rims were equivalent. This tool may help surgeons remove well-fixed cups in a short time and reduce the deforming load on the bone around the cup without increasing the size of the subsequent reconstruction cup.

To identify the best conditions for hot deformation, it is necessary to design innovative alloy systems. Data on flow stress and strain under various hot working scenarios are critical for creating processing (Hot Workability) maps. The deformation characteristics of Ti71Fe25.15Sn3.85 ternary alloys were explored through hightemperature compression experiments by a Gleeble (R) simulator at different temperature (700 degrees C, 800 degrees C, 900 degrees C, and 950 degrees C) with strain rates of 0.01 s- 1, 0.1 s- 1, and 10 s- 1. The alloy exhibited a fine eutectic structure composed of beta-Ti and FeTi phases, alongside coarse dendritic Ti3Sn and FeTi phases. Five machine learning (ML) models were employed for predicting the flow curve for another strain rate 1 s-1 and generating processing maps. The random forest (RF) model shows exceptional accuracy an R2 (coefficient of determination) of 96.7 %, RMSE (root mean square error) of 9.6 %, and MAE (mean absolute error) of 6.4 %.