Search Results (4,448)

Integration of thermographic imaging with in situ scanning electron microscopy (SEM) analysis may aid in quantifying thermal–mechanical behavior during tensile testing of 3D-printed polymers, which gives information about fracture mechanics, including the associated thermal phenomena. Upon fracture, samples exhibit changes in the thermal field, which is interesting because temperature fluctuations can affect material integrity. The paper introduces printing parameters to demonstrate a thermal measurement system’s sensitivity in detecting variations in mechanical response due to controlled changes in the process. Employing scientific methods, one can extrapolate results to a wider class of materials such as thermoplastics. Analysis of variance (ANOVA) is key in the design of experiments (DOE) if one wants to analyze the effect of factors and interactions. It has been used with the purpose of reducing the risk of type I errors (i.e., false positives). The finite element method (FEM) highlights temperature distribution in the area of interest and confirms recorded data. The particularly developed research experiments are carried out in a laboratory environment. Different samples are subjected to tensile tests under the evaluation of changes in the thermal field. SEM analysis is also widely used in fracture analysis to understand failure modes (ductile vs. brittle, crazing, delamination, and others). Thus, the paper aims to present a custom setup comprised a thermal camera pointed at samples during tensile testing that would serve as a reliable assessment system that accounts for the substitution of a sensor-based environment but is still fully capable of validating the measurement approach. Full article

Partial differential equations are an integral part of modern scientific development. Hyperbolic partial differential equations are encountered in many fields and have many applications—both linear and nonlinear types, with some being semilinear and quasilinear. In this paper, a family of implicit numerical schemes for solving hyperbolic partial differential equations is derived, utilizing finite differences and tridiagonal sweep. Through the discrete Fourier transform, a necessary and sufficient condition for convergence is proven for the linear version of the family of difference schemes, expanding the known results on boundary conditions that ensure convergence. Numerical verification confirms the found condition. A series of experiments on different boundary conditions and semilinear hyperbolic PDEs show that the same condition seems to also hold in those cases. In view of the results, an optimal subset of the family is found. A comparison between the implicit schemes and an explicit analogue is conducted, demonstrating the gained efficiency of the implicit schemes. Full article

Finite element analysis has been widely applied in restorative dentistry, but there is limited evidence directly comparing the biomechanical behavior of amalgam and bulk-fill composite resins in standardized cavity designs. This study aimed to evaluate the stress distribution in enamel, dentin, and restorative materials under different cavity configurations and filling materials. A 3D model of a maxillary molar was reconstructed from dental tomography using Geomagic Design X 2020. Four cavity models were created with Solidworks 2013: Class I (occlusal, Group A), Class II disto-occlusal (Group B), Class II mesio-occlusal (Group C), and Class II mesio-occluso-distal (Group D) cavities. Each model was restored with either amalgam or bulk-fill composite and a 600 N occlusal force was applied. Maximum principal stresses were analyzed with ABAQUS software. The highest stress was observed in the bulk-fill composite restoration of the Class II MO cavity (231 Mpa), whereas the lowest stress occurred in amalgam restoration of Class I cavity. Overall, amalgam restorations showed lower stress concentrations than bulk-fill composites, especially in complex cavity designs. These results suggest that cavity configuration and restorative material selection influence stress distribution and may impact the long-term biomechanical stability of restored teeth. Full article

The purpose of this in silico study was to evaluate the main difference of the adhesion strength of direct and semi-direct composite resin restorations in dentin using micro-tensile testing (μTBS) and finite element analysis (FEA). This in silico study employed cohesive zone traction and shear laws to investigate interfacial damage in both restoration groups. Tridimensional finite element models of both restoration specimens were created. A 20 μm thick resin cement layer was created for the semi-direct case. The Clearfil SE Bond 2 adhesive system and the restorative material, Ceram X Spectra ST HV composite resin, were used on both restorations. The numerical bond strength of both restoration techniques was evaluated using two different analysis assumptions. In the first assumption, the numerical analysis procedure included only the non-linear behavior of dentin and the von Mises damage criterion, whereas cohesive zone models were included in the second analysis assumption. The influence of dentin-adhesive cohesive mechanical properties was studied using values reported in the literature, and a sensitivity study helped improve the correlation between experimental and numerical results. The mechanical properties of the composite cohesive zone were defined assuming that the interface strength of dentin and composite follows the values reported by the manufacturer of Spectra ST. Damage initiation and progression were analyzed, and strains and stresses of the cohesive zone models (CZM) were compared with the corresponding perfect bonded models. The experimental µTBS results for the direct restoration strategy showed an adhesive strength of 38.156 ± 10.750 MPa, while the CZM predicted a slightly higher value of 40.4 ± 10.8 MPa. For the indirect restoration strategy, the experimental adhesive strength was 25.449 ± 10.193 MPa, compared to a numerically predicted strength of 28.1 ± 9.3 MPa. Overall, the CZM tends to overestimate the adhesive strength relative to experimental values. The statistical analysis of dentin extension strains for direct (DR) and semi-direct (SR) group models reveals that the SR configuration yields higher strain levels. Hence, these results suggest that, assuming identical dentin properties across both restoration groups, the material configuration in the direct restoration offers better mechanical protection to the dentin. These findings highlight the critical role of incorporating damage mechanics to more accurately characterize stress distribution during tooth rehabilitation. Full article

To reduce welding deformation during the automated welding of thick-walled pipes in shipbuilding and thereby improve welding quality, a segmented multi-layer multi-pass welding sequence optimization and process improvement strategy is proposed. Firstly, based on a welding model for thick-walled pipes, a multi-layer multi-pass welding trajectory equation is established. A double-ellipsoidal moving heat source is adopted to design a circular multi-layer multi-pass double-ellipsoidal heat source model. Secondly, three circular pipe workpieces with different wall thicknesses are selected, and four segmented welding sequences are simulated using welding finite element analysis (FEA). Finally, based on the optimal segmented welding sequence, the welding process is improved, and optimal welding process parameters are determined based on deformation and residual stress analysis. The results of the segmented multi-layer multi-pass welding sequence optimization show that the skip-symmetric welding method yields the best results for thick-walled circular pipes. Compared to other welding sequences, it reduces welding deformation by an average of 6.50% and welding stress by an average of 5.37%. In addition, process improvement tests under the optimal welding sequence indicate that the best welding quality is achieved under the following conditions: for 10 mm thick pipes—200 A current, 24 V voltage, and 11.5 mm/s welding speed; for 15 mm thick pipes—215 A, 24.6 V, and 10 mm/s; and for 20 mm thick pipes—225 A, 25 V, and 11 mm/s. Full article

Frequent building fires seriously threaten the safety of steel structures. According to the data, fire accidents account for about 35% of the total number of production safety accidents. The collapse of steel structures accounted for 42% of the total collapse. The early warning problem of steel structure fire collapse is imminent. This study aims to address this challenge by establishing a novel early warning framework, which is used to quantify the critical early warning threshold of steel frames based on elastic modulus degradation and its correlation with ultrasonic wave velocity under different collapse modes. The sequential thermal–mechanical coupling numerical method is used in the study. Firstly, Pyrosim is used to simulate the high-fidelity fire to obtain the real temperature field distribution, and then it is mapped to the Abaqus finite element model as the temperature load for nonlinear static analysis. The critical point of structural instability is identified by monitoring the mutation characteristics of the displacement and the change rate of the key nodes in real time. The results show that when the steel frame collapses inward as a whole, the three-level early warning elastic modulus thresholds of the beam are 153.6 GPa, 78.6 GPa, and 57.5 GPa, respectively. The column is 168.7 GPa, 122.4 GPa, and 72.6 GPa. Then the three-level warning threshold of transverse and longitudinal wave velocity is obtained. The three-stage shear wave velocity warning thresholds of the fire column are 2828~2843 m/s, 2409~2434 m/s, and 1855~1874 m/s, and the three-stage longitudinal wave velocity warning thresholds are 5742~5799 m/s, 4892~4941 m/s, and 3804~3767 m/s. The core innovation of this study is to quantitatively determine a three-level early warning threshold system, which corresponds to the three stages of significant degradation initiation, local failure, and critical collapse. Based on the theoretical relationship, these elastic modulus thresholds are converted into corresponding ultrasonic wave velocity thresholds. The research results provide a direct and reliable scientific basis for the development of new early warning technology based on acoustic emission real-time monitoring and fill the gap between the mechanism research and engineering application of steel structure fire resistance design. Full article

During the cooling phase of injection molding, the conformal cooling channel system optimizes the uniformity of mold temperature, diminishes warping deformation, and contributes substantially to heightened product precision. The injection molding process involves complex process parameters that may result in uneven cooling between components, leading to prolonged cycle times, increased shrinkage depth, and warping deformation of the plastic parts. These manifestations negatively impact the surface quality and structural strength of the final product. This article combined theoretical algorithms with finite element simulation (CAE) methods to optimize complex injection molding processes. Firstly, the characteristics of six different types of materials were examined. Melt temperature, mold opening time, injection time, holding time, holding pressure, and mold temperature were chosen as optimization variables. Meanwhile, the warpage deformation and shrinkage depth of the formed sample were selected as optimization objectives. Secondly, an L27 orthogonal experimental design (OED) was established, and the signal-to-noise ratio was processed. The entropy weight method (EWE) was used to calculate the weights of the total warpage deformation and shrinkage depth, thereby obtaining the grey correlation degree. The influence of process parameters on quality indicators was analyzed using grey relational analysis (GRA) to calculate the range. A second-order polynomial regression model was established using response surface methodology (RSM) to investigate the effects of six factors on the warpage deformation and shrinkage depth of injection molded parts. Finally, a comprehensive comparison was made on the impact of various optimization methods and models on the forming parameters. Analyze according to different optimization principles to obtain the corresponding optimal process parameters. The research results indicate that under the principle of prioritizing warpage deformation, the effectiveness ranking of the three optimization analyses is RSM > OED > GRA. The minimum deformation rate is 0.1592 mm, which is 27.37% lower than before optimization. Under the principle of prioritizing indentation depth, the effectiveness ranking of the three optimization analyses is OED > GRA > RSM. The minimum depth of shrinkage is 0.0312 mm, which is 47.21% lower than before optimization. This discovery provides strong support for the optimal combination of process parameters suitable for production and processing. Full article

The growing concerns over nuclear power plant safety in the wake of extreme impact events have highlighted the need for containment structures with superior resistance to large commercial aircraft strikes. Conventional reinforced concrete containment has shown limitations in withstanding high-mass and high-velocity impacts, posing potential risks to structural integrity and operational safety. Addressing this challenge, this study focuses on the dynamic impact resistance and vibration behavior of steel–ultra-high-performance concrete (S-UHPC) composite containment, aiming to enhance nuclear facility resilience under beyond-design-basis aircraft impact scenarios. Validated finite element models in LS-DYNA were developed to simulate impacts from four representative large commercial aircraft types, considering variations in wall and steel plate thicknesses, UHPC grades, and soil–structure interaction conditions. Unlike existing studies that often focus on isolated parameters, this work conducts a systematic parametric analysis integrating multiple aircraft types, structural configurations, and foundation conditions, providing comprehensive insights into both global deformation and high-frequency vibration behavior. Comparative analyses with conventional reinforced concrete containment were performed, and floor response spectra were evaluated to quantify high-frequency vibration characteristics under different site conditions. The results show that S-UHPC containment reduces peak displacement by up to ~24% compared to reinforced concrete of the same thickness while effectively localizing core damage without through-thickness failure. In addition, aircraft impacts predominantly excite 90–125 Hz vibrations, with soft soil conditions amplifying acceleration responses by more than four times, underscoring the necessity of site-specific dynamic analysis in nuclear containment and equipment design. Full article

This study investigates the influence of electrical actuation parameters on the performance of a morphing composite aerodynamic profile actuated by Shape Memory Alloy (SMA) wires. A fully coupled electro-thermo-mechanical finite element model has been developed to simulate the transient response of NiTi SMA, capturing the nonlinear interplay between temperature evolution, phase transformation, and mechanical deformation under Joule heating. The model incorporates phase-dependent material properties, heat effects, and geometric constraints, enabling accurate prediction of actuation dynamics. To validate the model, a morphing spoiler prototype has been fabricated using high-performance additive manufacturing with a carbon fibre-reinforced polymer. The SMA wires have been pretensioned and electrically actuated at different current levels (3 A and 6 A), and the resulting deformation has been recorded through video analysis with embedded timers. Experimental measurements confirmed the model’s ability to predict both actuation time and displacement, with maximum deflections of 33 mm and 40 mm corresponding to different current inputs. This integrated approach demonstrates an efficient and compact solution for active aerodynamic surfaces without the need for mechanical linkages, enabling future developments in adaptive structures for automotive and aerospace applications. Full article

Micro-computed tomography (micro-CT) is a commonly used tool for bone evaluation in animal model research. Micro-scale finite element analysis (µFEA) has been proposed to account for different loading scenarios, detailed three-dimensional (3D) bone structure, material properties, and distribution obtained from micro-CT to estimate bone mechanical properties and to predict its potential fracture. The in vivo application of µFEA has been limited to animal models due to the smaller bore size of micro-CT and the long scan time. This narrative review article describes studies that used micro-CT-based µFEA to predict bone mechanical competence, understand bone fracture and remodeling mechanisms, and to evaluate the impacts of the therapeutics, implants, and surgical interventions. Moreover, the concept, limitations, and future potentials of micro-CT-based FEA are discussed. Full article

The dynamics of mechanical systems with fast motions and dynamic loads are strongly influenced by the deformability of kinematic elements. The finite element method and the superposition of rigid body motion with deformable body motion allow us to determine a new structure for the matrices that define the mechanical system equations of motion. Meshing the kinematic elements into finite elements causes the unknowns of the problem to no longer be displacement functions but rather nodal displacements. These displacements are considered as a linear combination of modal shapes and modal coordinates. This method is applied to a drive mechanism of an internal combustion engine with three pistons mounted in line. The system is driven by the pressure exerted by the gas on the piston head, which was experimentally determined. The longitudinal and transversal deformations of the connecting rod are determined, including the nodal displacements. These results were verified through virtual prototyping on the 3D model, using multibody system theory and the finite element method. The recorded differences are mainly explained by the type, size, and shape of the used finite elements. Experimental analysis allows us to determine the connecting rod kinematic and dynamic parameters as functions of time and frequency variation. The developed method is flexible and can be easily adapted to systems with fast motions in which, during operation, impact forces appear in joints for various reasons. Full article

To enhance design efficiency, this study employs an effective prediction approach that utilizes validated finite element analysis (FEA) to generate simulation data and subsequently applies machine learning (ML) techniques to predict packaging reliability. Validated FEA models are used to replace the costly design-on-experiment approach. However, the training time for some ML algorithms is costly; therefore, reducing the size of the training dataset to lower computational cost is a critical issue for ML. Nevertheless, this approach simultaneously introduces new challenges in maintaining prediction accuracy due to the inherent limitations of small data machine learning. To address these challenges, this work adopts Wafer-Level Packaging (WLP) as a case study. It proposes an ensemble learning framework that integrates multiple machine learning algorithms to enhance predictive robustness. By leveraging the complementary strengths of different algorithms and frameworks, the ensemble approach effectively improves generalization, enabling accurate predictions even with constrained training data. Full article

Duct fan motors must provide high torque within limited space to maintain airflow while requiring low vibration characteristics to minimize fluid resistance caused by fan oscillation. Axial Flux Permanent Magnet Motor (AFPM) offers higher torque performance than Radial Flux Permanent Magnet Motor (RFPM) due to their large radial and short axial dimensions. In particular, the coreless AFPM structure enables superior low-vibration performance. Conventional AFPM typically employs a core-type stator, which presents manufacturing difficulties. In core-type AFPM, applying a multi-stator configuration linearly increases winding takt time in proportion to the number of stators. Conversely, a Printed Circuit Board (PCB) stator AFPM significantly reduces stator production time, making it favorable for implementing multi-stator topologies. The use of multi-stator structures enables various topological configurations depending on (1) stator placement, (2) magnetization pattern of permanent magnets, and (3) rotor arrangement—each offering specific advantages. This study evaluates and analyzes the performance of different topologies based on efficient arrangements of magnets and stators, aiming to identify the optimal structure for duct fan applications. The validity of the proposed approach and design was verified through three-dimensional finite element analysis (FEA). Full article

Additive manufacturing technology, specifically material extrusion, offers great potential for scaffold manufacturing in tissue engineering. This study presents a novel methodology for the design and optimization of 3D printed polymeric scaffolds to enhance cell viability, thereby promoting improved cell proliferation for tissue engineering applications. Different infill patterns, including gyroid, parallel sinusoidal, and symmetric sinusoidal, were evaluated to determine their impact on cell proliferation and tissue regeneration. To overcome the limitations of existing slicer software, a novel open-source software called FullControl GCode Designer was utilized, enabling the creation of customized infill patterns without restrictions. VOLCO software was employed to generate voxelized 3D models of the scaffolds, simulating the material extrusion process. Finite element analysis was conducted using Abaqus software to evaluate the mechanical properties of the different designs. Additionally, new scripts were developed to evaluate the interconnectivity and pore size of the voxelized models. A factorial design of experiments and a genetic algorithm (combined with Kriging metamodels) were applied to identify the optimal configuration based on optimization criteria (keeping the mechanical stiffness and pore size within the recommended values for trabecular bone and maximizing the surface and interconnectivity). Biological testing was conducted on polylactic acid scaffolds to preliminarily validate the effectiveness of the modeling and optimization methodologies in this regard. The results demonstrated the agreement between the optimization methodology and the biological test since the optimum in both cases was a symmetric sinusoidal pattern design with a configuration resulting in a structure with 53.08% porosity and an equivalent pore size of 584 µm. Therefore, this outcome validates the proposed methodologies, emphasizing the role of pore surface area and interconnectivity in supporting cell proliferation. Overall, this research contributes to the advancement of AM technology in tissue engineering and paves the way for further optimization studies in scaffold design. Full article

To study the vibration characteristics of viscoelastic slurry pipe structures under fluid–structure interaction (FSI), we constructed a three-dimensional FSI pipe model based on the finite element method to systematically investigate the effects of fluid effects, pipe length, and wall thickness on the vibrational characteristics of viscoelastic slurry pipes. A modal analysis demonstrated that fluid effects not only significantly reduced the natural frequency of the pipe but also disrupted the symmetry of the vibration modes and eliminated the phenomenon of frequency degeneracy. The frequency reduction caused by FSI reached 54%, which was dominant compared with the water-attached effects, and its impact intensified with the increasing vibration order. The water-attached effect exhibited differences between odd and even orders, attributed to the influence of vibration modes on the distribution of fluid inertial forces, with a contribution of 45.07% to 55.24% in the odd orders and of only 37.69% to 38.93% in the even orders. When the FSI and water-attached effects acted together, the frequency reduction was further aggravated, but the reduction ratio did not follow a simple linear superposition. The parametric analysis of the pipe showed that when the pipe length increased from 1 m to 3 m, the growth rate of its natural frequency was only 26.52% that of the shorter pipe, indicating that the longer the pipes, the slower the growth rate of frequency. When the wall thickness increased from 5 mm to 11 mm, the growth rate of the first-order natural frequency decreased from 15.43% to 7.44%, suggesting that the frequency improvement effect caused by the stiffness augmentation diminished with the increase in wall thickness. The research results hold significant guiding significance for the structural design of slurry pipe systems in practical engineering and the safe operation of pipe systems. Full article