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Thin-wall structures, particularly thin-walled tubes, play a critical role in load-bearing structures. Enhancing their ability to withstand crushing loads can significantly improve the overall damping efficiency of the system. Functionally graded thickness (FGT) is a promising approach for enhancing the load-bearing properties of thin-walled tubes by enabling control over material usage and localized deformation patterns within the structure. In this study, we proposed a novel theoretical model that analyzes the crushing behavior of hollow and foam-filled FGT thin-walled circular tubes by considering four primary failure mechanisms that contribute to energy dissipation: (1) bending of plastic hinges, (2) membrane stretching, (3) axial foam crushing, and (4) the interaction between foam and the tube's wall. We validated our model against experimental results from previous researchers and observed a good agreement. Additionally, we conduct a comprehensive study to examine the effects of various geometrical parameters, such as power-law functions and normalized wall thickness ratio, on the crushing behavior of FGT structures. Our results demonstrate the accuracy and reliability of our theoretical model and highlight the potential of FGT structures to enhance the performance of thin-walled tubes in a range of load-bearing applications.

The riveting process involves numerous parameters and complex problems, such as contact phenomena and material nonlinearity; therefore, it is challenging to accurately control the deformation of riveted parts by adjusting the riveting parameters. Therefore, this paper proposes a global sensitivity analysis method to determine the effects of riveting parameters on the maximum deformation of aeronautical thin-wall structures (ATWS). Considering the correlation among variables, the riveting parameters are used as input variables and the maximum deformations of ATWS are used as the output response to establish a high-precision second-order random sampling-high dimensional model representation response function. The structure and correlative sensitivity analysis method is then used to analyze the response function, and an importance ranking of the input variables is obtained to provide guidance for designs that reduce the riveting deformation of thin-walled plates.

Purpose Additive manufacturing based on arc welding is a fast and effective way to fabricate complex and irregular metal workpieces. Thin-wall metal structures are widely used in the industry. However, it is difficult to realize support-free freeform thin-wall structures. This paper aims to propose a new method of non-supporting thin-wall structure (NSTWS) manufacturing by gas metal arc welding (GMAW) with the help of a multi-degree of freedom robot arm. Design/methodology/approach This study uses the geodesic distance on the triangular mesh to build a scalar field, and then the equidistant iso-polylines are obtained, which are used as welding paths for thin-wall structures. Focusing on the possible problems of interference and the violent variation of the printing directions, this paper proposes two types of methods to partition the model mesh and generate new printable iso-polylines on the split meshes. Findings It is found that irregular thin-wall models such as an elbow, a vase or a transition structure can be deposited without any support and with a good surface quality after applying the methods. Originality/value The experiments producing irregular models illustrate the feasibility and effectiveness of the methods to fabricate NSTWSs, which could provide guidance to some industrial applications.

In this study, we analyzed the coupling effect of laser scanning speed and wall thickness on the phase transformation behavior and tensile properties of selective laser melted NiTi thin-wall structures. It is demonstrated that either scanning speed or wall thickness has their respective influence rule, whereas this influence could be changed when coupling them together; that is, under different scanning speeds, the effect of wall thickness could be different. It is found that the deviation of phase transformation temperature among different wall thicknesses is ~3.7 °C at 400 mm/s, while this deviation increases to ~23.5 °C at 600 mm/s. However, the deviation of phase transformation peak width among different wall thicknesses shows little change under different scanning speeds. At low scanning speed, the samples with thicker wall thickness exhibit better tensile ductility than thinner, whereas they all show poor tensile properties and brittle behavior at high scanning speed. This uncertain influence rule is mainly due to the interaction effect between different thermal histories generated by wall thickness and scanning speed.

The advanced capabilities of directed energy deposition (DED) technology in manufacturing are expected to be utilized in production of thin wall structures. However, to unlock its full potential, research and development of the DED technology is required. The goal of this study was to investigate the effects of height of thin wall structure and deposition strategies on thermo-mechanical characteristics of G6 powder deposited on SCM440 substrate via a DED process. This study used finite element analysis (FEA) methods to simulate the deposition process. Laser heat source with Gaussian distribution was adopted for this study. Temperature dependent properties of G6 and SCM440 along with properties of air and shielding gas, were used for accurate estimations of temperature field during the deposition process. The changes in stress, displacement and distortion are discussed. Additionally, the effects of dwell time and preheating on thermo-mechanical characteristics of thin wall structures are compared.

The single-pass multi-layer depositing strategy is usually used to fabricate thin-wall structures with wire and arc additive manufacturing (WAAM) technology. Various deposited wall thicknesses often lead to a change in arc shrinkage in the wall thickness direction, which affects the arc shape and stability, and even the microstructure and properties. To systematically study the effect of wall thickness (δ) on arc shape and stability, 3D numerical models were established, with wall thickness varying from 1 to 14 mm during the WAAM process. The characteristics of the arc shape, temperature field, velocity field, current density, and the electromagnetic force were investigated. When δ is smaller than the arc diameter (Φ), the thinner wall will result in a longer arc along the deposition direction. When δ is greater than the Φ, the arc shape tends to be a bell shape. When δ < Φ, the peak temperature in the arc centre, the peak current density, and the electromagnetic intensity along the welding direction decreased with the increase in the wall thickness. However, the opposite observations were found when δ < Φ. The simulation results are consistent with the actual arc shape collected and showed that when δ is slightly less than Φ, the forming quality of the deposited wall is the best. The research in this paper can fill the research gap and provide a theoretical basis for the matching selection of process parameters and wall thickness in WAAM applications.

During the plastic forming process, the change of loading mode directly affects the deformation condition of the material. In this study, two forming methods are applied in the forming process of the thin-walled structure with external cross-ribs. The forming characteristics differences between the point loading mode and the line loading mode were investigated in terms of material flow behavior, stress-strain distribution, and forming uniformity. The results indicate that the non-essential axial deformation was reduced and the directional deformation was accomplished by the line loading mode. Compared to the point loading mode, the forming loading was reduced by approximately 30%. The material deformation mainly focused on the surface region of the workpiece since the loading deformation area was small under the point loading mode, and the part showed a significant delamination deformation and stress concentration. However, under the line loading mode, these phenomena can be improved. The radial equivalent strain gradient of the external cross-ribs formed by the line loading mode is about 1/3 of that by the point loading mode. Additionally, the height discrepancy of transverse ribs between the spin-in and spin-out sides was reduced under the fixed diversion surface, and the forming uniformity of the external cross-ribs was improved.

With the continuous development of the protective structures and the upgrading of blast mitigation materials, traditional shaped charge warheads are gradually difficult to cause effective damage to heavily armoured ships. To improve the penetration capability of the warhead and achieve large aperture damage to the structures, Annular Shaped Charge (ASC) with unique geometric structure is proposed and applied. In order to investigate the damage effect of the ASC on thin-walled structures with near-field explosion, a series of numerical calculations are carried out based on the Coupled Eulerian-Lagrangian (CEL) method. The influence of the standoff distance on the penetration performance of the ASC is analysed, and the optimal standoff distance is also obtained. Moreover, the influence of medium on the penetration ability of the ASC is explored. The process of jet formation and penetration of the ASC in air medium, water medium and water with an air cavity are compared and analysed. The results show that water not only limits the formation effect of the ASC, but also significantly reduces the jet tip velocity. Accordingly, an air cavity is added in front of the liner to improve the formation effect of the ASC. As a result, both the formation effect and the penetration ability of the ASC in water are significantly improved, and the radius of the penetration hole is greatly increased.

In this paper, based on the evolution of bamboo structures, hexagonal, curved, and circular structures are proposed, and a new hierarchical design is proposed. The quasi-static compression experiment of the three structures was carried out respectively, and the energy absorption performance of the three structures was analyzed and discussed by comparing the results. The results show that the energy absorption properties are curved structure, hexagonal structure, and circular structure from high to low. On this basis, by layering the hexagonal structure evenly in ten layers and setting different printing parameters for each layer, a total of 12 hierarchical structures are designed. Quasi-static compression experiments are carried out on these hierarchical structures, and they are compared with uniform hexagonal structures and curved structures. The results show that the energy absorption performance of all hierarchical structures is improved by 42.67% compared with uniform print structures, and 4.97%-33.07% compared with curved structures. This research can provide a new idea and reference for the hierarchical design of 3D printing energy-absorbing structures.

The aerospace community widely uses difficult-to-cut materials, such as titanium alloys, high-temperature alloys, metal/ceramic/polymer matrix composites, hard and brittle materials, and geometrically complex components, such as thin-walled structures, microchannels, and complex surfaces. Mechanical machining is the main material removal process for the vast majority of aerospace components. However, many problems exist, including severe and rapid tool wear, low machining efficiency, and poor surface integrity. Nontraditional energy-assisted mechanical machining is a hybrid process that uses nontraditional energies (vibration, laser, electricity, etc) to improve the machinability of local materials and decrease the burden of mechanical machining. This provides a feasible and promising method to improve the material removal rate and surface quality, reduce process forces, and prolong tool life. However, systematic reviews of this technology are lacking with respect to the current research status and development direction. This paper reviews the recent progress in the nontraditional energy-assisted mechanical machining of difficult-to-cut materials and components in the aerospace community. In addition, this paper focuses on the processing principles, material responses under nontraditional energy, resultant forces and temperatures, material removal mechanisms, and applications of these processes, including vibration-, laser-, electric-, magnetic-, chemical-, advanced coolant-, and hybrid nontraditional energy-assisted mechanical machining. Finally, a comprehensive summary of the principles, advantages, and limitations of each hybrid process is provided, and future perspectives on forward design, device development, and sustainability of nontraditional energy-assisted mechanical machining processes are discussed. A topical review of nontraditional energy-assisted mechanical machining is introduced. The advantages and limitations of each hybrid machining process are addressed. Perspectives on forward design, device development, and sustainability are discussed.