ABSTRACT Pultrusion of hollow composite profiles with fast‐curing polyurethane (PU) resin requires simultaneous control of heat transfer, cure kinetics, viscosity evolution, and pulling resistance, making empirical process optimization costly and uncertain. This work develops a multifidelity thermo–chemical–mechanical modeling framework for hollow glass‐fiber (GF) and carbon‐fiber (CF)‐reinforced PU profiles produced on an industrial PulFlex pultrusion line. Three complementary model tiers are integrated using a common physics backbone: a one‐dimensional (1D) mathematical model for rapid parametric screening, a two‐dimensional (2D) homogeneous finite element model in ABAQUS for process‐scale response, and a three‐dimensional (3D) laminate‐resolved finite element model in ANSYS for fiber‐architecture and through‐thickness gradient prediction. All models employ Kamal–Sourour cure kinetics, Di Benedetto vitrification, cure‐dependent rheology, and cure‐hardening instantaneously linear elastic modulus evolution to predict temperature, degree of cure, viscosity, glass‐transition temperature, and pulling force along a multizone heated die. Embedded thermocouple measurements are used to calibrate the 1D thermal history and to independently evaluate the 2D and 3D thermal predictions at the reference condition, whereas differential scanning calorimetry‐derived degree‐of‐cure data provide an independent check on cure progression for all three model tiers. The models reveal distinct thermochemical behavior between GF and CF systems and quantify the accuracy‐versus‐cost tradeoff across fidelities. Under the tested three‐zone heater configuration, the multifidelity comparison identifies the speed range over which die‐exit cure, vitrification location, and predicted pulling resistance remain favorable for stable hollow‐profile manufacturing. The calibrated 1D model supports efficient process screening and future digital‐twin integration.
ABSTRACT The aluminum (Al) alloy double‐wire variable‐polarity double‐pulsed gas metal arc welding (DW‐VP‐DP‐GMAW) process integrates the advantages of VP and DP welding based on the DW‐GMAW process, thereby increasing the welding deposition rate and efficiency while controlling the heat input. Droplet transfer is a critical process that determines the weld formation quality. To elucidate the influences of the electrode negative (EN) ratio and DP on droplet transfer, a droplet force model was established based on the static force balance model (SFBM). The droplet transfer process was observed using high‐speed photography, and characteristic parameters, including droplet detachment time, transfer time, droplet size, and the probability of two droplets per pulse (TDPP), were systematically analyzed. The results showed that the introduction of direct current electrode negative (DCEN) polarity could eliminate explosive transfer and significantly reduce the probability of TDPP. With the increase in the EN ratio, the droplet diameter increased from 1.2 to 2.0 mm, the detachment time prolonged from 4 to 7 ms, and the transfer time increased from approximately 5 to 10.5 ms. DP reduced the amount of molten metal by decreasing the wire feed speed (15%–20% lower than that of a single pulse (SP)), which further optimized the stability of droplet transfer and reduced the probability of TDPP by more than 30%.
ABSTRACT Because of its high convergence rate for high‐frequency errors and conforming polishing capability, active fluid jet polishing (A‐FJP) has become a vital technology for the processing of optical components. The quality of optical components is usually evaluated by surface roughness (SR), directly influencing their optical performance and practical application effectiveness. For an in‐depth understanding of the A‐FJP process and its impact on SR, a prediction model is proposed in this study to evaluate the SR of optical components. First, the motion path of individual abrasives and the velocity distribution of the pad were modeled. Subsequently, a pressure distribution model was developed through fluid–structure interaction simulation. The material removal volume (MRV) per single abrasive and the number of effective abrasives were calculated. Models for both macroscale and microscale MRV were constructed separately. Ultimately, an A‐FJP roughness prediction model considering multiple process parameters was proposed. This model was validated through orthogonal process experiments. The results indicate that the maximum prediction error is 9.31%. An orthogonal experiment was conducted; through the analysis of variance, it was found that under the optimal process parameters, the SR decreased by 54.74% compared to the minimum value before optimization. The influence order of process parameters on SR is as follows: jet pressure > polishing time > spindle speed. These results verify the accuracy of the model and provide practical guidance for effectively controlling SR in A‐FJP.
ABSTRACT Small‐to‐micro‐sized inclined hole array are key geometric features in turbine blades of aero engine. In abrasive water flow finishing of such hole arrays, nonuniform dynamic fluid pressure distribution across hole walls lead to inconsistent finishing results. To address this problem, a novel method is proposed in this study for improving finishing consistency across the inclined holes by determining the appropriate processing parameters based on fluid dynamic pressure distribution. In the first stage, the correlation between fluid dynamic pressure and polishing results, that is, material removal and surface roughness, on the hole wall has been theoretically and experimentally investigated. Then, prediction models have been developed to establish a relationship between fluid dynamic pressure and polishing results via limited simple experiments in vertical holes. Afterward, it has been extended to optimize the machining time for inclined hole arrays to minimize the deviation in inter‐hole finishing results of inclined hole arrays using calculated dynamic pressure distribution on the hole wall. Model validation showed that the relative deviations of surface roughness and material removal from their target values were within 13%. The average Ra was reduced from pre‐polishing 5.2 μm to post‐polishing 1.45 μm, that is, a decline of 72.12%, and the Ra deviations among holes were controlled within ± 12%. This research shows that the proposed method can effectively improve finishing consistency of inclined hole array and can be extended to polish cooling holes of turbine blade.
Bioinspired architectures offer an effective strategy for enhancing the mechanical and functional properties of composite materials. In this study, 3D-printed Bouligand structures were designed and fabricated to investigate the correlation between hierarchical geometry, mechanical behavior, and piezoelectric potential when integrated with Rochelle Salt (RS) crystals. The Bouligand scaffolds, composed of helicoidally stacked lamellae with interlayer rotation angles of 4 deg, 14 deg, 22 deg, and 30 deg, were printed using a resin-based additive manufacturing process and subsequently infused with RS crystals grown in situ for 24 h from a saturated aqueous solution. Mechanical testing was conducted using uniaxial compression and three-point bending to evaluate the effect of layer rotation. The 22-deg configuration exhibited an optimal balance between stiffness and energy absorption, achieving an average compressive strength of similar to 300 N and bending load of similar to 100 N, together with enhanced fracture toughness due to efficient stress redistribution and crack deflection. After RS crystal growth, all reinforced samples showed a 20-35% increase in stiffness and improved interfacial cohesion, confirming the reinforcing effect of the crystalline phase. Piezoelectric measurements revealed that the 4-deg structure generated the highest voltage output (similar to 0.41 V), attributed to more direct stress transfer to the RS domains, while larger rotation angles led to lower output but superior mechanical resilience. These findings highlight a tunable trade-off between mechanical toughness and piezoelectric efficiency governed by the helicoidal rotation. This work establishes a sustainable, lead-free design approach that integrates piezoelectric crystal growth with bioinspired 3D-printed architectures, providing a promising platform for mechanically robust and energy-harvesting materials in wearable electronics and smart protective systems.
