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The objective of this study was to analyze the elastic critical local buckling of cold‐formed lipped channel sections using the energy method. A mechanical model and unique displacement functions simulating the local buckling behavior were proposed to consider the plate element interaction. Using the proposed mechanical mode, an analytical formula for local buckling that directly reflects the parameters of the channel member was proposed. Based on the proposed formula, the relationship between the cross‐sectional geometry and local buckling behavior was investigated. In addition, a simplified design equation was proposed. The reliability and effectiveness of the proposed equations were presented by comparing with the results of eigenvalue analysis based on the finite element method. The objective of this study was to analyze the elastic critical local buckling of cold‐formed lipped channel sections using the energy method. A mechanical model and unique displacement functions simulating the local buckling behavior were proposed to consider the plate element interaction. Using the proposed mechanical mode, an analytical formula for local buckling that directly reflects the parameters of the channel member was proposed. Based on the proposed formula, the relationship between the cross‐sectional geometry and local buckling behavior was investigated. In addition, a simplified design equation was proposed. The reliability and effectiveness of the proposed equations were presented by comparing with the results of eigenvalue analysis based on the finite element method.

The fracture mechanical behaviour of thin-walled structures with cracks is highly significant for structural strength design, safety and reliability analysis, and defect evaluation. In this study, the effects of various factors on the fracture parameters, crack initiation angles and plastic zones of thin-walled cylindrical shells with cracks are investigated. First, based on the J-integral and displacement extrapolation methods, the stress intensity factors of thin-walled cylindrical shells with circumferential cracks and compound cracks are studied using linear elastic fracture mechanics, respectively. Second, based on the theory of maximum circumferential tensile stress of compound cracks, the number of singular elements at a crack tip is varied to determine the node of the element corresponding to the maximum circumferential tensile stress, and the initiation angle for a compound crack is predicted. Third, based on the J-integral theory, the size of the plastic zone and J-integral of a thin-walled cylindrical shell with a circumferential crack are analysed, using elastic-plastic fracture mechanics. The results show that the stress in front of a crack tip does not increase after reaching the yield strength and enters the stage of plastic development, and the predicted initiation angle of an oblique crack mainly depends on its original inclination angle. The conclusions have theoretical and engineering significance for the selection of the fracture criteria and determination of the failure modes of thin-walled structures with cracks.

Distortional buckling of channel members is a critical factor in steel structures composed of thin‐walled members; however, existing models have limitations in accurately predicting this behavior. This study analyzes the distortional buckling behavior of channel members using an energy method. A nonconventional mechanical model and displacement functions are introduced to simulate distortional buckling behavior, highlighting the limitations of conventional models. An evaluation formula for the elastic distortional buckling strength is derived, directly reflecting the geometrical parameters of the channel member using the proposed mechanical model. Additionally, a design equation is formulated. The proposed evaluation formula and simplified design equation enable the precise determination of the elastic critical distortional buckling strength, including cases where distortional buckling is initiated by local buckling of the web, which previous evaluation formulas could not address. These methods enable continuous evaluation of distortional buckling in channel members. The proposed formula and design equation were verified against finite element analysis results, confirming their reliability and effectiveness. The developed model and equations offer improved accuracy over conventional approaches for predicting distortional buckling in channel members, demonstrating their reliability and applicability under diverse conditions. This study analyzes the distortional buckling behavior of channel members using an energy method. A nonconventional mechanical model and displacement functions are introduced to simulate distortional buckling behavior, highlighting the limitations of conventional models. An evaluation formula for the elastic distortional buckling strength is derived.

Thin-walled structures, like aircraft skins and ship shells, are often several meters in size but only a few millimeters thick. By utilizing the laser ultrasonic Lamb wave detection method (LU-LDM), signals can be detected over long distances without physical contact. Additionally, this technology offers excellent flexibility in designing the measurement point distribution. The characteristics of LU-LDM are first analyzed in this review, specifically in terms of laser ultrasound and hardware configuration. Next, the methods are categorized based on three criteria: the quantity of collected wavefield data, the spectral domain, and the distribution of measurement points. The advantages and disadvantages of multiple methods are compared, and the suitable conditions for each method are summarized. Thirdly, we summarize four combined methods that balance detection efficiency and accuracy. Finally, several future development trends are suggested, and the current gaps and shortcomings in LU-LDM are highlighted. This review builds a comprehensive framework for LU-LDM for the first time, which is expected to serve as a technical reference for applying this technology in large, thin-walled structures.

There are many deviation sources in the assembly process of aircraft complex thin-walled structures. To get important factors that affect quality, it is crucial to diagnose the key deviation resources. The deviation transfer between deviation sources and assembly parts has the characteristics of small sample size, nonlinearity, and strong coupling, so it is difficult to diagnose the key deviation sources by constructing assembly dimension chains. Therefore, based on the deviation detection data, transfer entropy and complex network theory are introduced. Integrating the depth-first traversal algorithm with degree centrality theory, a key deviation diagnosis method for complex thin-walled structures is proposed based on weighted transfer entropy and complex networks. The application shows that key deviation sources that affect assembly quality can be accurately identified by the key deviation source diagnosis method based on complex networks and weighted transfer entropy.

The interfacial bonding strength of the two deposited layers under the material extrusion process is always considered a shortcoming in the 3D-printed part. To address this issue, an extra polymer coating is added to the extruded filament by adding another self-designed nozzle concentrically to the original nozzle on the 3D printing head. Three filaments were used in the fabrication process: continuous carbon fiber as reinforcement filament, polylactic acid (PLA) filament as polymer substrate filament, and carbon nanotube (CNT)/PLA filament as polymer coating filament. In addition, the effect of CNT concentration on the 3D-printed thin-walled cylinder CNT/PLA/continuous carbon fiber (CF) composite was investigated by compressive buckling tests. Compared with 3D-printed thin-walled cylinder PLA/CF composite, the buckling loads were enhanced by 16.7%, 32.5%, 40.7%, and 50.1% under 5 wt%, 10 wt%, 15 wt%, and 20 wt% CNT concentration in the PLA polymer filament. This new 3D printing design creates a new possible solution to strengthen the 3D-printed part and can border the application of 3D-printed parts by varying polymer coating type through modifying the nanofiller-modified polymer filament.

Although topology optimization is well established in most engineering fields, it is still in its infancy concerning highly non-linear structural applications like vehicular crashworthiness. One of the approaches recently proposed and based on Hybrid Cellular Automata is modified here such that it can be applied for the first time to thin-walled structures. Classical methods based on voxel techniques, i.e., on solid three-dimensional volume elements, cannot derive structures made from thin metal sheets where the main energy absorption mode is related to plastic buckling, folding and failure. Because the main components of car structures are made from such thin-walled beams and panels, a special approach using SFE CONCEPT was developed, which is presented in this paper.

Inspired by the macro- and microstructures of the lotus leaf, a series of biomimetic hierarchical thin-walled structures (BHTSs) was proposed and fabricated, exhibiting improved mechanical properties. The comprehensive mechanical properties of the BHTSs were evaluated using finite element (FE) models constructed in ANSYS, which were validated by the experimental results. Light-weight numbers (LWNs) were used as an index to assess these properties. The simulation results were compared with the experimental data to validate the findings. The compression results indicated that the maximum load carried by each BHTS was very similar, with the highest bearing load being 32,571 N and the lowest being 30,183 N, resulting in only a 7.9% difference between them. In terms of the LWN-C values, the BHTS-1 exhibited the highest value at 318.51 N/g, while the BHTS-6 had the lowest value at 295.16 N/g. For the torsion and bending results, these findings suggested that increasing the bifurcation structure at the end side of the thin tube branch significantly improved the torsional resistance properties of the thin tube. For the impact characteristics of the proposed BHTSs, enhancing the bifurcation structure at the end of the thin tube branch significantly increased the energy absorption capacity and improved the energy absorption (EA) and the specific energy absorption (SEA) values of the thin tube. The BHTS-6 had the best structural design in terms of both the EA and SEA among all the BHTSs, but its CLE value was slightly lower than that of the BHTS-7, indicating slightly lower structural efficiency. This study provides a new idea and method for developing new lightweight and high-strength materials as well as designing more effective energy absorption structures. At the same time, this study has important scientific value in understanding how biological structures in nature exhibit their unique mechanical properties.

Topology optimization methods, as a crucial tool in the conceptual design phase of structures, can obtain the optimal load transfer path under specific loading and constraint conditions, making it an effective approach for lightweight structural design in aerospace engineering. This paper reviews recent research and advancements in topology optimization methods applied to aerospace structural design. Specifically, it summarizes recent developments in the topology optimization of structures subjected to design-variable-dependent loads (e.g., aero-engine disks and blades, aircraft wings), thin-walled structures, composite material structures, and fail-safe topology optimization designs. These structures and design concepts are representative of aerospace structural design. Additionally, the paper outlines future research directions, existing challenges, and technical difficulties, providing references for enhancing the application of topology optimization techniques in future aerospace structural design.