Search Results (152)

Channels with three standard symmetrical sections and one asymmetric section are mounted as cantilever beams with the web oriented vertically. A classical solution to the analysis of stress in each thin-walled cantilever channel is provided using the principle of wall shear flow superposition. The latter is coupled with a further superposition between axial stress arising from bending and from the constraint placed on free warping imposed at the fixed end. Closed solutions for design are tabulated for the net shear stress and the net axial stress at points around any section within the length. Stress distributions thus derived serve as a benchmark structure for alternative numerical solutions and for experimental investigations. The conversion of the transverse free end-loading applied to a thin-walled cantilever channel into the shear and axial stress that it must bear is outlined. It is shown that the point at which this loading is applied within the cross-section is crucial to this stress conversion. When a single force is applied to an arbitrary point at the free-end section, three loading effects arise generally: bending, flexural shear and torsion. The analysis of each effect requires that this force’s components are resolved to align with the section’s principal axes. These forces are then considered in reference to its centroid and to its shear centre. This shows that axial stress arises directly from bending and from the constraint imposed on free warping at the fixed end. Shear stress arises from flexural shear and also from torsion with a load offset from the shear centre. When the three actions are combined, the net stresses of each action are considered within the ability of the structure to resist collapse from plasticity and buckling. The novelty herein refers to the presentation of the shear flow calculations within a thin wall as they arise from an end load offset from the shear centre. It is shown how the principle of superposition can be applied to individual shear flow and axial stress distributions arising from flexural bending, shear and torsion. Therein, the new concept of a ‘trans-moment’ appears from the transfer in moments from their axes through centroid G to parallel axes through shear centre E. The trans-moment complements the static equilibrium condition, in which a shift in transverse force components from G to E is accompanied by torsion and bending about the flexural axis through E. Full article

In this work, a novel analytical equation is developed to accurately predict the mechanical behavior of thin-walled beams. The FEM was used for building the model and obtaining the results. The new equation developed is useful for the calculation of the displacement of a beam simply supported at its ends subjected to torsion loads, applied in opposite side areas of the Finite Element Method (FEM) model. The software Eureqa 1.24.0 was used to find hidden analytical models that were validated thereafter. The aim is to provide a formula that makes possible the comparison of analytic calculations with numerical calculations on bending and torsion combined load. A FEM model of a hollow-box beam with rectangular cross-section loaded with torsion was built and analytical calculations were performed. The analytic calculations were compared with the numeric results in order to know if the results are approximated. The results show good agreement. In the future, other models, such as internally reinforced beams, could also be tested with this methodology. Also, different conditions could be applied to the model studied in this work in order to evaluate the limitations and validity of the developed analytical model. Full article

Digital twin models utilising point cloud data have received significant attention for efficient bridge maintenance and performance assessment. There are some studies that show finite element (FE) models from point cloud data. While most of those approaches focus on modelling by solid elements, modelling of some civil structures, such as bridges, requires various uses of beam and shell elements. This study proposes a systematic approach for constructing shell element FE models from point cloud data of thin-walled structural members. The proposed methodology involves k-means clustering for point cloud segmentation into individual plates, principal component analysis for neutral plane estimation, and edge detection based on normal vector variations for geometric structure determination. Validation experiments using point cloud data of a steel corner specimen revealed dimensional errors up to 5 mm and angular errors up to 6°, but static load analysis demonstrated good accuracy with maximum displacement errors within 3.8% and maximum stress errors within 7.7% compared to nominal models. Additionally, the influence of point cloud data quality on FE model geometry and analysis results was evaluated based on geometric accuracy and point cloud density metrics, revealing that significant variations in density within the same surface lead to reduced neutral plane estimation accuracy. Furthermore, toward practical application to actual bridge structures, on-site measurements and quality evaluation of point cloud data from a steel plate girder bridge were conducted. The results showed that thickness errors in the bridge data reached up to 2 mm, while surface deviation RMSE ranged from 3 to 5 mm. This research contributes to establishing practical FE modelling procedures from point cloud data and providing a model validation framework that ensures appropriate abstraction in structural analysis. Full article

Background and Objective: Immature maxillary incisors (IMIs) are especially susceptible to failure due to their thin dentinal walls and compromised structural integrity following endodontic treatment. This study aims to evaluate the stress distribution within the root dentin after various post-endodontic treatments. Materials and methods: A personalized finite element analysis model of IMI was created using cone beam computed tomography (CBCT) data. Based on data from the literature, five stages of root development were reconstructed: half root development (S1), three-quarter development (S2), more than three-quarter development (S3), fully developed root with open apex (S4), and fully developed root with closed apex (S5). Six experimental groups were analyzed: GC Fiber Post (PS1); RelyX Post (PS2); metal post Unimetric 1.0 (PS3); everStick Post (PS4); positive control group with only the gutta-percha filling (PC), and intact maxillary incisor as negative control group (NC). The resulting equivalent stresses were evaluated using the Hencky–von Mises (HMH) strength theory. Results: The mean HMH stress within the root dentin was statistically significantly higher at the cervical level in all stages, except in stage S1 and models PS2 and PS3 in stage S2, where it was significantly higher at the apical level (p < 0.001 for all models, except stage S3 [PC model p < 0.005; NC model p < 0.008]). The PS4 model showed the lowest stress values at the cervical level in stages S1, S2, and S3 (55.19 MPa, 58.78 MPa, 58.84 MPa) and the PS1 model in stages S4 and S5 (57.48 MPa, 58.81 MPa). At the apical level, model PS3 showed the lowest stress values in stage S1 (69.60 MPa), model PS1 in stages S2, S3, and S5 (35.99 MPa, 44.30 MPa, 12.51 MPa) and model PC in stage S4 (17.85 MPa). Conclusions: The results showed that the greatest stress in an immature maxillary central incisor occurred at the cervical level, except during the early stage of root development. Post placement did not reduce root dentin stress. Full article

This paper presents the results of numerical investigations focused on a structural assembly consisting of thin-walled perforated steel beams joined to a particleboard panel. The simulations were performed using the finite element method (FEM), incorporating both physical and geometric nonlinearities, along with detailed modeling of contact interactions between the beams and panel elements. The primary objective was to establish load-capacity curves for the central beam in structural systems with spans ranging from 3 to 6 m, and to identify failure modes associated with different span lengths. To verify the reliability and accuracy of the numerical approach, laboratory tests were conducted on two representative configurations with spans of 3 and 6 m. Additionally, the mechanical properties of the beam materials were evaluated using samples extracted from the tested elements. The experimental findings confirmed the numerical model’s accuracy and its suitability for analyzing structural responses across the full span range considered. Full article

FLASH radiotherapy (FLASH-RT) is a cancer treatment delivering high-dose radiation within microseconds, reducing side-effects on healthy tissues. Implementing this technology at the PBP-CMU Electron Linac Laboratory poses challenges in ensuring radiation safety within a partially underground hall with thin walls and ceiling structures. This study develops a localized shielding design for electron beams (6–25 MeV) using the GEANT4 release 11.2.2 Monte Carlo simulation toolkit. A multilayer system of lead, iron, polyethylene, and concrete effectively attenuates X-rays, gamma-rays, and neutrons, achieving dose levels below 1 mSv/year for public areas and within 20 mSv/year for controlled areas, meeting international standards. The B-factor analysis highlights efficient low-energy gamma attenuation and thicker shielding requirements for high-energy rays. The design minimizes radiation leakage, ensuring safe operation for FLASH-RT while safeguarding personnel and the environment. Future work includes constructing and validating the system, with methodologies applicable to other electron beam facilities. Full article

Machining deformation is a key bottleneck that restricts the improvement of manufacturing accuracy of aviation thin-walled structural components, such as frames, beams, and wall panels. The initial residual stress of the workblank and the cutting load are the direct factors leading to machining deformation. Based on the initial residual stress measurement and the milling force test, a finite element prediction model for milling deformation of frame-type thin-walled parts with integrated consideration of initial residual stress and the milling force was established and experimentally verified in this study. Then, the influence of milling process factors, such as the frame processing sequence (FPS), the cutting path, and the single frame one-time removal depth (SFORD), on the milling deformation of frame-type parts was studied. The results showed that the established prediction model had high reliability and the prediction accuracy was improved by 6.7% compared with that when only considering the initial residual stress. A smaller machining deformation can be achieved through the use of the FPS to prioritize the width, direction, and symmetrical milling, as well as the inner loop cutting path, and the smaller SFORD. This study can provide a technical reference for the prediction and control of milling deformation of aviation thin-walled structural parts, especially frame-type thin-walled parts. Full article

A well-designed clamping layout significantly enhances the dynamic stiffness of a manufacturing system, improving its stability and suppressing cutting chatter in workpieces. This paper focuses on the machining of thin-walled beams, which are prone to vibration and have low stiffness, especially under hydraulic floating clamping conditions. By analyzing the system stability domain, we propose a method to improve system stiffness through strategic design of support module layouts. Finite element dynamic simulations and modal hammer experiments were conducted to validate this approach. The results show that the proposed layout design method increases the relative central frequency by 13.49% and the relative fundamental frequency by 8.51%. These findings demonstrate a substantial improvement in the dynamic stiffness of the part-clamping system, confirming that the auxiliary support module layout design method effectively enhances system dynamic stiffness and suppresses cutting chatter. Full article

Composite structures are increasingly being utilized in modern construction. This computational analysis focuses on the structural performance of composite beams formed by thin-walled, cold-formed steel channel sections strengthened with concrete. The primary objective of this research was to enhance the strength and stability of composite cold-formed steel beams. In this study, back-to-back C-channel sections and concrete slabs with various stiffener configurations were analyzed. The key parameters considered include stiffener spacing, type, and thickness. Additionally, different beam cross-sections, such as C-channel and sigma sections, were investigated. A finite element analysis was conducted using the ABAQUS program, incorporating both geometric and material nonlinearities. The developed models were validated against experimental results from previous research and existing design guidelines. Three beam specimens were examined in this study to assess their structural behavior under static loading conditions. A novel aspect of this research is the investigation of composite cold-formed steel beams under a combination of ultra-high-performance concrete (UHPC) and negative moment effects. The load–deflection behavior of all beam specimens was analyzed, considering variations in cross-sectional dimensions and span lengths. Additionally, the study highlights key material properties, including the maximum compressive strength of concrete, the yield strength of cold-formed steel channels, and the cross-sectional area of the steel components for each beam specimen. This research provides valuable insights for structural engineers, contributing to the optimization of composite cold-formed steel beam design for enhanced performance in practical applications. Full article

Metal inert gas (MIG) brazing was used to join galvanized thin sheets with thicknesses in the range of 0.8 to 2 mm in a lap joint configuration using CuAl₈ wire as filler. The process was used to manufacture built-up cold-formed steel beams composed of corrugated steel webs and flanges made from thin-walled cold-formed steel lipped channel profiles. The effect of heat input and sheet thickness on joint properties, such as macro- and microstructure, wettability, and mechanical characteristics such as microhardness and tensile strength were investigated. The bead geometry was assessed by studying the wettability of the filler material. The microstructure was investigated by digital and scanning electron microscopy, and the composition in the heat-affected zone (HAZ), interface, and bead was determined by energy dispersive spectroscopy. Formation of Fe–Al intermetallics was observed in the bead at the bead–base material interface. Some pores were noticed that formed due to the evaporation of the zinc coating. The bead shape and mechanical properties were found to be the best when 1.2 and 2 mm sheets were brazed using a heat input of 121.4 J/mm. This suggests that not only the heat input but also the thickness of the sheet metal play a crucial role in the production of MIG brazed joints. Full article

Conventional analyses often simplify vertical loads as uniform radial loads while neglecting axial force effects in the buckling analyses of arches, leading to discrepancies between theoretical predictions and actual loading conditions. To address this issue, this research proposes a nonlinear analytical approach based on asymptotic methods, include the parameter perturbation method and the Wentzel–Kramers–Brillouin (WKB) method. The results show the following: (1) The parameter perturbation method is effective for the snap-buckling of a shallow arch, and the fifth-order solution is sufficiently accurate. (2) For shallow arches with a large modified slenderness ratio, the influence of the axial load component cannot be neglected. (3) Regardless of the rise-to-span ratio of the arch, the nonlinear bending moment is significantly larger than the linear bending moment. (4) In the anti-symmetric buckling analysis, the eigenvalue obtained using the second-order WKB method is smaller than that obtained using the third-order WKB method; therefore, the second-order solution can be used as the critical load. (5) For shallow arches with a small rise-to-span ratio, the critical load for anti-symmetric buckling closely matches the classical solution, and the results from arches subjected to a uniformly distributed radial load are reliable. For deep arches with a large rise-to-span ratio, the influence of the axial load component cannot be ignored. Full article

The isothermal oxidation behavior of single crystal DD6 film-cooling blades was investigated. The isothermal oxidation tests were conducted at 1050 °C, and the phase analysis was performed by XRD, while SEM (EDS) was employed to observe the material. In addition to experimental studies, a numerical simulation using three-dimensional finite element analysis based on Abaqus software (Version 6.13) was implemented to model the growth stress in specimens during the isothermal test. The obtained results showed that the average oxidation rate of specimens rose with increments in film hole spacing, up to a maximum value at a film hole spacing of 0.75 mm, and then fell, which could be interpreted with the concepts of the oxidation-affected zone and the growth stress. The results obtained from the numerical simulation of the growth stress agreed with the experimental results of the average oxidation rate. The oxide scale of film-cooling specimens mainly consisted of three layers, the NiO outer layer, the spinel sublayer containing cracks, and the non-continuous thin Al₂O₃ inner layer. The surface of the oxide scale commonly underwent spallation of the NiO outer layer, and the exposed sublayer could grow new NiO particles. The size of the NiO particles on the edge of the film holes was larger than those on the walls of the film holes. SEM images clearly showed that electro-hydraulic beam drilling on DD6 superalloy specimens could erode the γ phase in the γ/γ′ two-phase matrix, thereby inducing damages in regions near film holes. Full article

In this study, we analyzed novel internally reinforced hollow-box beams to evaluate their strength using the finite element method (FEM) in ANSYS Mechanical APDL 18.1. Twelve different FEM models were subjected to static bending loads, and their performance was assessed based on Huber–Mises equivalent strength values. The results show that most optimized models exhibited improved strength compared to their initial versions, with some configurations achieving up to a 470% increase. These findings highlight the effectiveness of structural optimization in enhancing the strength behavior of hollow-box beams, providing valuable insights for engineering applications. Full article

The aim of this work is to develop and test an analytical model that is deemed to be more accurate than the traditional method in the prediction of the mechanical behavior of hollow box beams. The methodology was tested with a hollow box beam of a rectangular section. To achieve the aim, a new analytical model was derived. An FEM model of a simple box beam was built, and the results of the comparison between the classical theory, the novel equation, and the l numerical method are presented. It was possible to validate the new equation with the numerical model and the classical equation. It was observed that the novel equation can predict the mechanical behavior of the studied geometries with better accuracy than the classical equation. Full article

This study presents a novel optimization framework applying the multi-objective response surface method to enhance the safety of electric micro commercial vehicles (E-MCVs) during side pole impacts. By focusing on seven critical load-bearing components, including the B-pillar and door frame beam, we achieved a 2% reduction in component weight while significantly improving energy absorption by 22.2%. The optimization led to a substantial decrease in intrusion, with B-pillar abdominal intrusions reduced by 22.5% and lower threshold intrusions down by 26.3%. Despite these improvements, challenges remained regarding battery pack deformation. To address this, we proposed two innovative solutions: strengthening the side longitudinal beams and integrating a bionic thin-walled energy-absorbing structure. These approaches effectively reduced side intrusions of the battery pack by 43.5% to 43.8%, with the bionic structure showing superior performance in weight management. However, the manufacturing feasibility and cost implications of the bionic design necessitate further exploration. The innovation in this study lies in the dual application of a response surface optimization method for load-bearing components and the integration of biomimetic design principles, significantly advancing collision safety for E-MCVs while providing new insights into the weight-efficient safety design. Full article