Search Results (71)

To investigate the dynamic behavior of smart composite structures with embedded heat sources over a wide temperature range, this study employed thermoplastic polypropylene as the matrix, combined with glass/carbon fiber prepregs and Ni80Cr20 alloy heating wires, and fabricated functional laminated specimens with integrated heating elements via a prepreg molding process. Using a self-developed variable-temperature cantilever beam vibration testing system, the evolution of natural frequencies and damping ratios from room temperature to 140 °C was systematically examined. Results indicate that temperature-induced thermal softening of the polypropylene matrix reduces the effective bending stiffness of the composites, leading to a decline in natural frequencies across all modes. For example, the first-order natural frequency of the sample decreased from approximately 30.8 Hz at room temperature to about 28.3 Hz at 140 °C, representing a reduction of approximately 8.12%. The second-order reduction reached about 8.99%, and the third-order reduction was approximately 9.65%. Carbon fiber-reinforced specimens exhibited relatively smaller frequency reductions due to the high modulus of the fibers. Concurrently, elevated temperatures enhance molecular chain mobility and interfacial viscoelastic dissipation at the fiber–matrix interface, causing a sharp increase in damping ratios at high temperatures (>100 °C). For instance, the damping ratio of the first-order mode increased significantly from approximately 1.02% at room temperature to about 2.9% at 140 °C. By comparatively analyzing carbon fiber and glass fiber systems, the study elucidated the distinct mechanisms underlying the “fiber-dominated” stiffness retention effect and the “resin/interface-dominated” damping dissipation effect under thermal influence. These findings provide critical experimental data and theoretical references for the active thermal regulation of structural performance in thermoplastic composite structures with integrated heat sources, thereby mitigating damage caused by external disturbances. Full article

An accurate prediction of the final properties of injection-molded semi-crystalline parts requires models that capture crystallization kinetics during processing. This work presents two practical strategies to incorporate experimentally derived crystallization behaviors into Autodesk Moldflow, addressing cases where kinetics differ from the software’s native Avrami–Hoffman–Lauritzen formulation. We apply these methods to isotactic polypropylene (iPP T30G) displaying heterogeneous nucleation with a low-temperature plateau, and to polyoxymethylene (POM) exhibiting combined heterogeneous and homogeneous nucleation. The parameters for Moldflow were obtained by matching isothermal half-crystallization times (t_0.5) and by tuning flow-induced nucleation terms. Validation against isothermal and non-isothermal injection tests shows agreement between calculated and expected crystallinity evolution and reproduces measured spherulite diameters. Full article

Aluminum alloy 2024 (AA2024) is widely used in the aerospace sector, where a fine, uniform, and equiaxed grain structure is crucial for achieving enhanced mechanical properties. This study examines the effect of dynamic solidification, assisted by mechanical vibrations and conformal cooling, on the microstructural evolution and mechanical properties of permanent mold-cast AA2024. Mechanical vibrations were applied during solidification in the frequency range of 15–45 Hz and acceleration of 0.5–1.5 g. Process parameters, including pouring temperature, die temperature, vibration frequency, and acceleration, were optimized using an L9 orthogonal array based on the Taguchi method. Analysis of variance (ANOVA) was performed to determine the significance of the aforementioned process parameters. In addition, the alloy’s microstructure was observed through a microscope, which revealed a transition from dendritic to non-dendritic microstructure due to dynamic solidification. The average grain size of the alloy was significantly reduced by 40.9%. Moreover, the values of hardness and Ultimate Tensile Strength (UTS) of the alloy were improved by 13.5% and 10.6%, respectively. Optimal results were obtained at a pouring temperature of 750 °C, die temperature of 150 °C, frequency of 45 Hz, and acceleration of 1.0 g. Moreover, uncertainty analysis for all three responses was also performed. Full article

The growing demand for high-quality decorative polymer surfaces has increased interest in Out Mold Decoration (OMD), yet the combined influence of processing conditions and product geometry on film adhesion and deformation remains insufficiently defined. This study establishes an integrated framework that connects OMD process parameters with geometry-dependent deformation behavior using polycarbonate films printed with an ink grid. Adhesion and surface quality were evaluated using 2.5D specimens, while 3D models with varied fillet radii, slopes, and heights enabled quantitative assessment of grid-spacing evolution and thickness distribution. Results show that preheating smooths the film without improving adhesion, whereas increasing the forming environment temperature enhances both bonding and surface quality within the material’s thermal tolerance. Vacuum pressure strengthens film–substrate contact but requires moderation to prevent overstretching. An optimized condition of 100 °C preheating, 90 °C forming temperature, and 2.5 kg vacuum pressure provides a balanced performance. Geometric factors exert strong control over deformation, with small radii, steep slopes, and tall features producing greater strain and nonuniform thinning. These findings establish practical processing windows and geometry guidelines for achieving reliable OMD components that integrate high visual quality with stable adhesion performance. Full article

To address the demands of modern high-speed and high-quality continuous casting production, depositing high-performance coatings on the surface of mold copper plates is critically important for extending the service life of continuous casting molds. To this end, a Ni-Co-Cr/SiC nanocomposite coating was developed, and cryogenic treatment was applied to further improve its hardness and wear resistance. This work systematically investigates the microstructural evolution and performance enhancement of the Ni-Co-Cr/SiC nanocomposite coating under different cryogenic treatment parameters, with special emphasis on the effects of treatment temperature on the coating’s microstructure, hardness, wear resistance, and adhesion to the substrate. The results demonstrate that decreasing the cryogenic treatment temperature and extending the holding time effectively refine the grains of the coating while simultaneously promoting the accumulation of microstrain and dislocation density. These changes lead to significant improvements in hardness, wear resistance, and interfacial bonding performance. Specifically, after direct immersion at −196 °C for 16 h, the coating reached a hardness value of 946.5 HV, and the wear rate was reduced to 0.032 mm³·(N·m)⁻¹, representing only 54.6% of that of the untreated coating. The dominant wear mechanism transitioned to a mixed mode of abrasive wear and oxidative wear. Moreover, the cryogenic treatment enhanced the stability of the coating-substrate adhesion. Full article

Understanding the way samarium–cobalt alloys solidify at varying cooling rates and the regularities in alloying element distribution is crucial for optimizing subsequent homogenization and annealing processes, leading to an enhancement in the overall quality of the product. The study investigates the effects of rapid water-cooled copper mold (600 °C/min), medium-speed copper mold (100 °C/min), and slow furnace cooling (10 °C/min) on the microstructural evolution, element distribution, and phase transformation of samarium–cobalt (Sm-Co) alloys. The results of the research show that the phase transition temperatures obtained via differential scanning calorimetry (DSC) closely matched those observed in situ by high-temperature laser scanning confocal microscopy (HT-LSCM). Higher cooling rates resulted in notable dendritic refinement and reduced precipitate size. Elemental analysis revealed that Co and Fe exhibited negative segregation, whereas Sm, Cu, and Zr showed positive segregation, with segregation intensity increasing alongside the cooling rate. The principal phases identified included Cu-rich and Zr-rich constituents, the matrix phase, and a gray phase morphologically distinct from the matrix. These correspond to the (Sm, Co, Fe, Cu, Zr)₅ phase, (Sm, Zr)(Co, Fe, Cu)₃ phase, Sm₂(Co, Fe, Cu, Zr)₁₇ phase, and Sm(Co, Fe, Cu, Zr)₇ phase. The phase constitution remained consistent across different cooling rates. Full article

During the Fused Deposition Modeling (FDM) molding process, temperature changes are nonlinear and instantaneous, which is a key parameter affecting FDM printing efficiency, molding accuracy, warpage deformation, and other factors. This study presents a finite element simulation framework that integrates ANSYS Parametric Design Language (APDL) with birth–death element technology to investigate the temperature evolution and thermomechanical behavior during the FDM process. The framework enables dynamic simulation of the complete printing and cooling cycle, capturing the layer-by-layer material deposition and subsequent thermal history. Results indicate that temperature distribution follows a gradient pattern along the printing path, with rapid heat dissipation at the periphery and heat accumulation in the central regions. Thermomechanical coupling analysis reveals significant stress concentration at the part bottom (310 MPa) and progressive strain increase from bottom (3.68 × 10⁻⁵ m) to top (2.95 × 10⁻⁴ m). Experimental validation demonstrates strong agreement with numerical predictions, showing maximum temperature deviations below 8% and strain distribution errors within 5%. This integrated approach provides an effective tool for predicting thermal-induced deformations and optimizing FDM process parameters to enhance part quality. Full article

The deformation mechanism during the hot compression of PM nickel-based superalloy FGH99 and its micro-structural evolution, especially the evolution of γ’ phases, are the key factors affecting the final molding quality of aero-engine hot forged turbine disks. In this study, a new constitutive model of viscoplasticity with micro-structures as physical internal parameters were developed to simulate the hot compression behavior of FGH99 by incorporating the strengthening effect of the γ’ phase. The mechanical behavior of high-temperature (>1000 K) compressive deformation of typical superalloys under a wide strain rate (0.001~1 s⁻¹) is investigated using the Gleeble thermal-force dynamic simulation tester. The micro-structure after the hot deformation was characterized using EBSD and TEM. Work hardening as well as dynamic softening were observed in the hot compression tests. Based on the mechanical responses and micro-structural features, the model considered the coupled effects of dislocation density, DRX, and γ’ phase during hot flow. The model is programmed into a user subroutine based on the Fortran language and called in the simulation of the DEFORM-3D V6.1 software, thus realizing the multiscale predictive simulation of FGH99 alloy by combining macroscopic deformation and micro-structural evolution. The established viscoplastic constitutive model shows a peak discrepancy of 10.05% between its predicted hot flow stresses and the experimental values. For the average grain size of FGH99, predictions exhibit an error below 7.20%. These results demonstrate the high accuracy of the viscoplastic constitutive model developed in this study. Full article

Conventional grain monitoring systems often rely on isolated data points (e.g., point-based temperature measurements), limiting holistic condition assessment. This study proposes a novel Mechanism and Data Driven (MDD) framework that integrates physical mechanisms with real-time sensor data. The framework quantitatively analyzes solar radiation and external air temperature effects on silo boundaries and introduces a novel interpolation-optimized model parameter initialization technique to enable comprehensive grain condition perception. Rigorous multidimensional validation confirms the method’s accuracy: The novel initialization technique achieved high precision, demonstrating only 1.89% error in Day-2 low-temperature zone predictions (27.02 m² measured vs. 26.52 m² simulated). Temperature fields were accurately reconstructed (≤0.5 °C deviation in YOZ planes), capturing spatiotemporal dynamics with ≤0.45 m² maximum low-temperature zone deviation. Cloud map comparisons showed superior simulation fidelity (SSIM > 0.97). Further analysis revealed a 22.97% reduction in total low-temperature zone area (XOZ plane), with Zone 1 (near south exterior wall) declining 27.64%, Zone 2 (center) 25.30%, and Zone 3 20.35%. For dynamic evolution patterns, high-temperature zones exhibit low moisture (<14%), while low-temperature zones retain elevated moisture (>14%). A strong positive correlation between temperature and relative humidity fields; temperature homogenization drives humidity uniformity. The framework enables holistic monitoring, providing actionable insights for smart ventilation control, condensation risk warnings, and mold prevention. It establishes a robust foundation for intelligent grain storage management, ultimately reducing post-harvest losses. Full article

The efficient and high-quality welding for joining Invar alloy parts is imperative for the fabrication of composite material forming molds. The residual stress distributions and microstructural evolution during oscillating welding of Invar alloy remain inadequately characterized in the current literature, necessitating further comprehensive investigation. In this paper, laser oscillating welding with circle mode is carried out for 5 mm thick plates of Invar alloy. A finite element model for the laser oscillation welding process of Invar alloy has been established. The numerical simulations and experimental methodologies are synthetically carried out to investigate the influence of oscillating parameters on temperature field, residual stress field, and microstructure characteristics. Furthermore, the microstructural evolution of laser oscillating-welded Invar alloy is elucidated by correlating it with the characteristic distribution of the temperature field. Simulation results showed that the residual stress significantly decreases under the action of the oscillating laser. The increasing of the oscillation frequency and amplitude results in a more uniform distribution of the residual stress, and the stress peak shows a downward trend. It is indicated that the oscillation of the beam resulted in the formation of numerous fragmented fine crystals within the weld seam. Consequently, the tensile strength and elongation of the oscillating welded joint exhibit respective enhancements of 15.0% and 36.6% compared to the non-oscillating condition. Full article

In the light of increasing research into amorphous composites and their applications, as-cast specimens of multicomponent Ti₄₈Zr₁₈V₁₂Cu₅Be₁₇ amorphous composites were prepared via water-cooled copper mold suction casting. Subsequently, the as-cast specimens were subjected to semi-solid isothermal treatment to obtain semi-solid specimens. Taking the semi-solid specimens as the research object, room temperature compressive deformation behavior was investigated by analyzing the shear band characteristics on the side surfaces of the compressed specimens. The evolution of shear bands at various stages of plastic deformation was investigated via scanning electron microscopy (SEM). Additionally, significant work hardening was observed after yielding. Surface deformation morphologies indicate that the work-hardening behavior is associated with plastic deformation, interactions between shear bands, and interactions between shear bands and β-Ti crystals. Experiments have demonstrated that at a specific deformation extent, shear bands preferentially initiate at the crystal–amorphous matrix interface. In the final stage of plastic deformation, shear bands propagate through work-hardened β-Ti crystals into the amorphous matrix, with their propagation retarded by the β-Ti crystals. When shear bands in the amorphous matrix are obstructed by β-Ti crystals and can no longer propagate, some evolve into cracks. These cracks then propagate exponentially, leading to eventual fracturing of the specimens and termination of plastic deformation. The research findings provide a theoretical basis for analyzing the deformation capacities of various amorphous composites. Full article

This work investigates the time-dependent changes in temperature, flow, and solidification microstructure under various cooling conditions. The mechanism of the effects of different pouring temperatures on the morphology and evolution of the solidification microstructure is explored. During gradual cooling, the temperature distribution remained consistent and the solid–liquid interface extended to its furthest extent. In contrast, water cooling generated the most pronounced temperature gradient at the solidification front, which was conducive to the development of columnar grains. Specifically, the maximum solidification rates at the center of the casting under the water-cooled copper mold, copper mold, and ceramic mold conditions were 2.71 mm/s, 1.45 mm/s, and 0.95 mm/s, respectively, with water cooling achieving the fastest rate. In the early stages of solidification, the flow velocity at the casting center was relatively high, and during slow cooling, the molten material tended to flow toward the surface. When air cooling was applied, the molten material at the center migrated outward, while under water cooling, the fluid moved in an upward direction. At a heat transfer coefficient of 100 W/(m²·K), the alloy primarily formed equiaxed grains; however, at 5000 W/(m²·K), the proportion of columnar grains increased significantly, and the average grain area expanded from 3.664 × 10⁻⁶ m² to 4.441 × 10⁻⁶ m². Additionally, as the pouring temperature increased from 1100 °C to 1200 °C, the number of grains decreased, while the average radius grew from 1.665 × 10⁻³ m to 1.820 × 10⁻³ m, resulting in a reduced fraction of equiaxed grains. This study provides valuable theoretical insights for optimizing the solidification process of this particular alloy. Full article

Stretch blow molding (SBM) is widely utilized in industrial applications, yet the deformation characteristics of materials during this process are intricate and challenging to precisely articulate. To accurately forecast the stress–strain response of polyethylene terephthalate (PET) in SBM, a hybrid Artificial Neural Network (ANN)-based constitutive model has been developed. The model has been created by combining a physical-based function for capturing the small-strain behavior in parallel with an ANN-based model for capturing the temperature-dependent large-strain nonlinear viscoelastic behavior. The architecture of the ANN has been designed to ensure stability in a load-controlled scenario, thus making it suitable for use in FEA simulations of stretch blow molding. Data for training the model have been generated by a new semi-automatic experimental rig which is able to produce 850 stress–strain curves over a wide range of process conditions (temperature range 95–115 °C and strain rates ranging from 1/s to 100/s) directly from blowing preforms using a combination of high-speed video, digital image correlation and sensors for pressure and force. The model has already been implemented in the commercial FEA package Abaqus via a VUMAT subroutine, with its performance validated by comparing the prediction of the evolution of preform shape during blowing vs. high-speed images. In conclusion, the developed hybrid ANN model, when integrated into Abaqus, offers a more accurate simulation of SBM processes, contributing to improved design efficiency and product quality. Full article

Structural design usually adopts uniform temperature action. However, during the actual construction of the structure, the temperature field acting on the structure is inhomogeneous. Therefore, the simulation of the construction of statically indeterminate steel structures considering only the uniform temperature field cannot truly reflect the temperature action after structural molding and the evolution of the stress performance of the temporary stress system of structural construction. This paper proposes a force feedback method for the construction of statically indeterminate steel structures based on staged temperature measurements. In this method, the construction sequence and the measured temperature are taken into account, and the structural response under the action of temperature is obtained by using the first processing method in the matrix displacement method and the deformation coordination formula to obtain the deformation and stress values of the structure. The application results show that the structural forces calculated by the method proposed in this paper are closer to the measured data in the field, and the error is reduced by 10~40%. This paper provides a reference for the calculation of construction forces in statically indeterminate steel structures considering the effect of temperature inhomogeneity and provides a basis for construction safety assessment and schedule management. Full article

When exposed to different building environmental conditions, bio-composite materials, such as hemp mortars, represent a risk of mold proliferation. This later plays a critical role in the biodeterioration of the materials when their physical properties are locally modified by the natural aging process. The primary objectives of the present work are first to assess the evolution of the surface of contaminated mortar; second, to investigate an accurate DNA extraction method that could be used for both bio-composite mortars and their fiber sources collected in situ; then, to understand the process of the proliferation of mold strains on both hemp shives and hemp mortar; and finally, to compare mold strains present in these phases to show their relationship to mold contamination and their impact on human health. In situ hemp mortar contamination behavior was investigated in the region of Pau (France) two months after hemp mortar application in extreme conditions (high humidity, low temperature, no aeration), which did not match the standard conditions under which hemp mortar must be used. The SEM observations and FTIR and pH analyses highlighted the decrease in pH level and the presence of organic matter on the mortar surface. DNA sequencing results showed that hemp shives were the main source of fungal contamination of hemp mortar. A mold population analysis showed that the most dominant phylum was Ophistokonta, which represented 83.6% in hemp shives and 99.97% in hemp mortar. The Acrostalagmus genus representatives were the most abundant, with 42% in hemp shives and 96% in hemp mortar. The interconnection between the mold strain characteristics (particularly the ability to grow in extreme environments) and the presence of hemp mortar was emphasized. Full article