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Thin-walled plates are extensively used in the aerospace industry due to their lightweight properties. However, their low rigidity makes them susceptible to deformation and chatter during traditional machining processes, which increases machining complexity and reduces both quality and efficiency. Therefore, this paper proposes an electrochemical machining method involving the use of a rotating body with complex structured windows as the cathode, enabling pure rolling motion on the workpiece surface. Through the action of an electrolyte and an external power supply, the material is removed from the machined surface layer by layer in the form of ions, thus facilitating the manufacture of complex thin-walled plates. Based on the principles of this method, a kinematics model was established to determine the relative position relationship between the cathode and anode during machining. Additionally, an electric field model and a material dissolution model were established to analyze the electric potential distribution and simulate the process of material removal. The simulation results indicate that the trajectory of the cathode windows forms a "V" shape, with the taper angle being independent of the window angle, but decreasing as the cathode diameter increases. Furthermore, it was observed that the use of an insulation coating can effectively reduce stray corrosion on convex structures of the workpiece surface. Based on these simulation results, electrochemical machining experiments were conducted on nickel-based GH4169 plates measuring 600 × 96 mm with a thickness of 3 mm. The results demonstrate that the average thickness of machined workpieces is 1.1 mm, with a thickness error of 0.12 mm. Meanwhile, the surface roughness Ra is 0.778 μm, with a material removal rate reaching 1.01 cm3/min (8271.9 mg/min). Therefore, electrochemical machining proves to be an effective method for manufacturing thin-walled plates. [ABSTRACT FROM AUTHOR]

In this paper, the accurate free vibration characteristics of thin-walled box beam are discussed and the kinematic model is established by using fine shear deformation theory. The model adopts the in-plane and out-of-plane displacement fields including extension, torsion, warping and distortion, as well as the transverse shear due to bending and warping due to torsion. One-dimensional high-order beam theory is applied to the dynamic solution of thin-walled box beam, and the analytical solution of high free vibration modes of multi-deformation coupled modes under different boundary conditions is derived. The results show that warping, distortion and shear deformation play an important role in the free vibration characteristics of thin-walled box beam, and the validity of the model is verified. In addition, finite element software (ANSYS) is used for finite element simulation. The application of vibration mode in the structure design of thin-walled box beam is summarized, especially in the case of higher natural frequency. The calculation method is in good agreement with the finite element results. [ABSTRACT FROM AUTHOR]

Inspired by the tree fractal structure, a novel hexagonal hierarchical gradient tube with axial variable thickness (HHGAVT) is proposed and its crashworthiness performances are systematically investigated. Results show that when the axial variation coefficient of wall thickness k > 0, the peak crushing force (PCF) of HHGAVT will significantly decrease meanwhile the energy absorption maintains at a high level compared with the referenced structures under the same mass. When k > 0, the PCF and CFE of HHGAVT have absolute advantage compared with the uniform wall thickness tube. The crashworthiness performance can further increase by rational designing the distance factor δ. [ABSTRACT FROM AUTHOR]

This work presents a reduced-order solution for the thermoelastic geometrically nonlinear response of simply-supported thin-walled structures subjected to the purely thermal load. Previously, the reduced-order method was only applicable to the buckling problem with a fixed temperature value. Now, the method is reformulated to achieve the critical buckling temperature from the thermoelastic geometrically nonlinear buckling analysis. The thermal buckling problem is represented using the thermal expansion model and its equivalent mechanical model, respectively. For the equivalent mechanical model, the simply-supported constraints need to be partially released and the temperature field is converted to be a thermal load. The reduced-order model is constructed based on the improve Koiter theory for thermal buckling analysis of the equivalent mechanical model. The thermoelastic geometrically nonlinear response is traced using the reduced-order solution together with a predictor-corrector process. The reduced-order solution of the equivalent mechanical model is validated by fully nonlinear solution of the thermal expansion model. Various plates and shells are selected to demonstrate the accuracy and highly efficiency of the proposed method for thermal buckling analysis. [ABSTRACT FROM AUTHOR]

Metal/CFRP hybrid structures have been increasingly applied in the automotive industry due to their favorable weight-saving and crashworthiness. In this article, a nonlinear finite element (FE) model is established to study the axial crushing behavior of aluminum/CFRP thin-walled tube structures. A progressive damage constitutive model is employed to capture the intra-laminar response of composites; Johnson-Cook model is used to describe the crushing process of aluminum layers and a bilinear cohesive zone model is applied for modeling the inter-layer delamination during the collapse process. A user material subroutine VUMAT involving these damage models is coded and executed to attain the numerical solution based on ABAQUS/Explicit solver. The axial crushing processes of thin-walled tubes with different configurations are simulated, and the corresponding damage characteristics are analyzed thoroughly. The influence of aluminum layer arrangement and cross-sectional shape on the crashworthiness and energy absorption of thin-walled tubes is discussed, which provides a design basis for the application of energy absorption elements. [ABSTRACT FROM AUTHOR]

Thin-walled structures that serve as energy absorbers are widely used in the automotive industry, and it is well-known that they deform in a specific way under dynamic loading, forming plastic hinges along the yield line. The dynamic impact of these structures causes various phenomena that affect the formation of folds and, consequently, the dynamic response of the structure. The force-shortening curve, which is based on the unified crush efficiency indicators, is a key factor in determining the dynamic response of the structure. While there have been many studies on energy absorbers under static or quasi-static loading conditions, the effect of changing kinetic energy components (mass and velocity) on the obtained crush efficiency indicators is not as well understood. This article presents the results of experimental tests and nonlinear numerical simulations for eleven different initial conditions of the crashworthiness analysis. The tests showed a significant effect of changing the velocity and mass of the striker on the results obtained. Additionally, the nonlinear effect of the change in the velocity of the tup with respect to the peak force and total efficiency was demonstrated. [ABSTRACT FROM AUTHOR]

The non-uniform distributed pressure of impact wave is usually simplified into concentrated or uniform load equivalently in the optimization design of constrained layer damping structure. However, for the thin-walled structure, it becomes necessary to regard the load as a non-uniform distribution. In this paper, a topology optimization approach is proposed considering the blast load with non-uniform distribution, aiming to unveil its impact on optimization layouts and dynamic responses. Initially, the smoothed particle hydrodynamics (SPH) algorithm is used to obtain the blast pressure what are extracted and integrated into the optimization model. Subsequently, the relative density is regarded as design variable. The construction of material penalty model and the topology optimization model are based on polynomial interpolation scheme (PIS). The sensitivity of objective function is deduced employing an improved adjoint variable method (AVM) to fit the load forms, and the Newmark- β method is used to calculate the dynamic response. The optimization criterion (OC) is adopted to update the design variables. Finally, two numerical examples are used to exhibit the validity and accuracy of the presented methodology. The findings indicate that the distributed form, spread velocity, excited position and excited amplitude of the blast load all exert a notable influence on optimization results and dynamic response. These results underscore the valuable engineering application of this research and introduce a fresh perspective to the challenge of topology optimization under the blast case. [ABSTRACT FROM AUTHOR]

AbstractThe study addresses piezoelectric actuator placement for active vibration control using an open-access framework that couples ANSYS and Python. It outlines a three-stage procedure: creating a finite element model in ANSYS APDL, using Python to determine the objective function, and applying a genetic algorithm optimization to find optimal actuator locations. Numerical simulations on plates and thin-walled conical structures demonstrate the effectiveness of the approach, showing it efficiently finds optimal placements with minimal search time and energy requirements. The study provides open-access codes for the framework, enhancing its accessibility and reproducibility. [ABSTRACT FROM AUTHOR]

Hybrid fibre reinforced polymer (FRP)-timber (HFT) thin-walled structural members are a novel technology developed recently as a sustainable alternative to thin-walled steel and aluminium structures. HFT structures are made by forming thin timber veneers and FRP laminates into efficient cross-sectional geometries. While existing studies have demonstrated the potential of HFT thin-walled members to be used as structural elements, a systematic study to investigate the behaviour of HFT thin-walled structures is yet to be carried out. This paper presents a study aimed at investigating the behaviour of HFT C-section columns under concentric axial loading. In total five HFT C-section specimens each from 700 mm to 2000 mm lengths were fabricated and tested. It was found that shorter HFT C-section columns failed due to local buckling while increase in length changed the failure mode to global buckling. Effect of GF orientation and density on load carrying capacity of the HFT C-section columns was investigated numerically. It was found that it's necessary to provide adequate GF volume in transverse to axis direction, but further increase in GF volume in transverse direction did not significantly increase the load carrying capacity. Increase in GF density in parallel to axis direction increased the load carrying capacity. [ABSTRACT FROM AUTHOR]

Thin-walled metal structures are known as an effective solution in absorbing impact energy and reducing the resulting reaction forces. The design of energy absorbers with higher energy absorption capability, lower weight and reaction forces, as well as lower manufacturing cost, has always been of interest. In this study, the effects of diameter and thickness of thin-walled Aluminum tubes on different crashworthiness criteria were investigated. To this end, different geometries were examined by simulating the uniaxial compressive test applying the finite element method. The results revealed that the optimal diameter for a simple circular tube (SCT), assuming constant length and thickness, is the smallest diameter in terms of resistance to global buckling. The SCT with an optimal diameter has the highest specific energy absorption (SEA), the lowest maximum crushing force ( F max ), and the highest crushing force efficiency (CFE). Moreover, in this study, the effect of thickness on the tubular absorber performance was numerically investigated according to four criteria: SEA, F max , CFE, and energy absorption (EA), and the optimal dimensions were obtained. Based on the results, increasing the thickness increases CFE, and increasing the ratio of thickness to diameter (t/D) increases SEA and CFE. Eventually, by applying the regression analysis, two equations were presented to calculate F max and CFE, which can be used to predict the performance of thin-walled metal tubes. Reducing the tube diameter reduces the force fluctuations during crushing. SEA increases by increasing the tube thickness specially for small diameters. As thickness-to-diameter ratio (t/D) increases, SEA and CFE increase. Three different objective functions were carried out to find the optimum tube. Obtained fitted equations predict the maximum crushing force and force efficiency. [ABSTRACT FROM AUTHOR]

Honeycombs are widely used in engineering protection, while the gap between peak and mean stresses remains to be narrowed, and the interaction effects among walls are weak. To break these limits, gradient curved‐walled honeycombs have been proposed recently. However, their in‐plane crashworthiness has never been studied, which restricts the actual applications in complex load environment. For this purpose, this article adopts experiments, finite‐element simulations, and theoretical analysis to reveal in‐plane crash performance of gradient curved‐walled honeycombs. Quasistatic and dynamic experiments are carried out for 3D‐printed honeycomb specimens made of 316L stainless steel, and numerical simulations are conducted by ABAQUS/Explicit. Compared to traditional straight‐ and curved‐walled honeycombs, gradient curved‐walled honeycombs display stabler deformation mode and more efficient mechanical response. Their EA and SEA are respectively 25.5% and 6.4% larger than straight‐walled honeycombs, and their energy absorption and force efficiencies are nearly 2.4 and 5.3 times larger, respectively. On this basis, plastic hinge model with high accuracy has been established, to derive the analytical solutions of their force–displacement relations. This work extends the comprehensive properties and application prospects of gradient curved‐walled honeycombs and sets an example to develop plastic hinge analysis with effective simplification and desirable accuracy on complex‐shaped structures. [ABSTRACT FROM AUTHOR]

Steel racking systems are widely adopted for storage purposes: they are thin-walled structures composed of consecutive trusses, connected with beams on which the palletized goods are stored. Their geometry and structural configuration strongly depend on market and operator necessities, and, in modern applications, racks can also function as the supporting structure of the warehouse itself in the form of Rack Supported or High-Bay Warehouses. With the increase of the overall geometric dimensions and the global weight of the stored material, the seismic action becomes more relevant for the design. Along these lines, the development and experimental testing of a dedicated seismic design approach for ductile steel racks is here presented, with particular attention to Rack Supported Warehouses. This approach exploits the ductility of trusses introduced via the plastic ovalization mechanism of the diagonal-to-upright connections while a tailored capacity design is used to assure the elastic behaviour of the rest of the structure and to keep the brittle failure mechanisms at bay. [ABSTRACT FROM AUTHOR]

Directed energy deposition (DED), as an additive manufacturing technology, has shown unique advantages in multi-material additive manufacturing and remanufacturing. In this study, two types in-situ alloyed CrCoNi medium entropy alloys that have thin-walled structures with different thicknesses (T1 and T2) were manufactured by the DED process, and the mechanisms of differences in relative density, microstructure, and mechanical properties at different heights were systematically analyzed. In terms of microstructure, the T1 and T2 samples along the building direction exhibit significant differences in crystallographic orientation, grain size, and dislocation density, which are related to the local temperature gradient differences caused by the scanning path and heat accumulation. In terms of mechanical properties at different heights of the two types of thin-walled structures, the yield strength is higher but the elongation is lower at the bottom position of sample, while the yield strength is lower but the elongation is higher at the middle and top positions. The differences of mechanical properties at different heights of the T1 and T2 samples are related to the microstructure and relative density. This finding provides new insights for the design and performance analysis of complex thin-walled structures formed by additive manufacturing. [ABSTRACT FROM AUTHOR]

AbstractThis study proposes two innovative thin-walled structures: the spiral tube (ST) and the multi-cell spiral tube (MCST), with MCST demonstrating better energy absorption performance. Through numerical simulation, geometric parameters of MCST are analyzed for their effect on crashworthiness performance. MCST with inner diameter of 15 mm, rotating angle of 4π, pitch of 18 mm and 6 ribs has the best energy absorption performance, and the SEA of MCST increases by up to 16.2% compared to the multi-cell circular tube, indicating superior energy absorption performance. The findings promote the optimization and application of structures in automotive energy absorption components. [ABSTRACT FROM AUTHOR]

Bio-inspired cellular structures provide excellent elements and design concepts for designing thin-walled energy-absorbing structures of vehicles, trains and aircrafts, due to their special structural characteristics and excellent mechanical properties. This study conducts a literature review of bio-inspired cellular energy-absorbing structures with a double-circular shape and multi-objective optimization problems of energy-absorbing structures. A multi-stage cooperative optimization algorithm, which combines the theories of multi-objective optimization and multi-criteria decision making, is proposed for solving the selection and optimization problems of bio-inspired cellular thin-walled structures. Multi-performance characterization analysis and evaluation of seven types of bio-inspired cellular structures under impact loading are carried out, including horsetail grass, bamboo, lotus leaf vein, beetle elytra, lotus root and shrimp dactyl club. Subsequently, comparative analysis and discussion are conducted to verify that this optimization method is feasible and practical. The results show that the optimized results obtained by this proposed algorithm are reliable, and the optimized bio-inspired cellular thin-walled energy-absorbing structure shows better overall characteristics in collisions. [ABSTRACT FROM AUTHOR]

In order to improve the crashworthiness of traditional Thin-Walled Struct, a new method for designing multicellular tubes is presented in this paper. In this work, multicellular columns based on origami centripetal folding method (MCOCFM) are proposed. The cross section of MCOCFM is designed in the way of origami. The mechanical properties of MCOCFM under uniaxial compression are analyzed by numerical simulation. Studies have shown that increased levels and wall thickness facilitate energy absorption. In addition, the theoretical prediction of MCF is in good agreement with the simulation results. Compared with some existing structures, MCOCFM has better crashworthiness. [ABSTRACT FROM AUTHOR]

The thin-wall effect of single crystal superalloys refers to the phenomenon that when the thickness of the sample and the part is less than 1 mm, the lasting life is reduced, the creep rate is increased and other mechanical properties are significantly attenuated. With the development of the internal cooling structure of advanced aero-engine single crystal blade parts, the structural thickness of some areas decreases, making it a typical thin-walled structure. Thus, it is of great engineering significance to consider the thin-wall effect in the thin-wall region during the design and manufacture of blades. Creep performance is one of the most important properties of superalloys for turbine blade application. This paper summarizes the thin-wall effect in creep performance of the superalloys as well as some advanced experimental equipment in the study of thin-wall effect. Research on thin-wall debit effect of superalloys can be divided into two categories, one is the cause of thin-wall debit, including the relative enhancement of oxidation, more significance in anisotropy, changes in micro structure and the initiation or growth of defects, and the factors that influence the thin-wall debit effect including experimental conditions (temperature, stress, etc.), the processing methods (casting, machining), geometric shape (rectangular cross-section, ring cross-section, film cooling holes). Research on thin-wall debit effect is within the scope of engineering application, as a part of "component level/analog component level" in "building block" verification and evaluation technology, thin-wall debit effect research under service environment or near-service environment conditions is more valuable for application. For this purpose, a variety of advanced experimental equipment platforms have been developed to simulate one or several coupled service conditions (high temperature, high pressure, corrosion/erosion, centrifugal loading) of the blade in the engine. Future research on thin-wall effects should be carried out under conditions closer to actual service conditions by preparing specimens according to the actual blade manufacturing process and conducting experiments on the equipment that simulates the service environment. [ABSTRACT FROM AUTHOR]

Introducing open holes or triggers in the crashworthy structures to reduce the weight or enhance the crash performance became popular. For this reason, this paper aims to answer the next question: To what extent can the trigger mechanisms influence the crashworthiness performance and failure mode of 3D-printed poly-lactic acid (PLA) square tubes for crashworthy applications? Consequently, four design parameters (trigger shape, number of triggers per face, depth of the trigger, and trigger position), each with three levels, were utilized for this goal. The planned tubes are being created using a 3D printing technique and then exposed to quasi-static axial compression loading. The crashing load and the absorbed energy against displacement responses were offered, as well as the failure histories being traced. The crashworthiness exploration was carried out by assessing various crash indicators, i.e., initial peak crash load F ip , total energy absorbed (U), specific absorbed energy (SEA), mean crash load ( F m ), and crash force efficiency (CFE). Additionally, the best triggering combinations are examined through the use of the complex proportional assessment (COPRAS) multi-attribute decision-making (MADM) method. According to the results, the studied parameters have appositive significance on the crashworthiness performance of 3D-printed square tubes. In light of the COPRAS findings, S3/8 T represents the best triggering mechanisms for crashworthy structures subject to axial compression loading. To put it in a nutshell, presenting triggers have a substantial effect on the crashworthiness performance of the square tubes. [ABSTRACT FROM AUTHOR]

Additive technologies, also known as 3D printing technologies, are becoming more and more widely used in industrial conditions for the production of finished elements, especially for the production of parts that would be very difficult or even impossible to produce using existing technologies. Technologically difficult elements include parts with a thin-walled spatial structure. This work presents the research results and describes the problems of producing specimens of thin-walled profiles filled with an appropriate spatial structure, also thin-walled, using 3D printing technology. The results of a three-point bending test of specimens of various lengths and specimens filled with chemically cured resin are presented. Print simulations were discussed, paying attention to problems related to applying lines and layers in FDM/FFF technology and the impact of print technological parameters on the properties of the manufactured specimens. [ABSTRACT FROM AUTHOR]

Thin-walled structures, i.e. the wing-upper-skin panels, are prone to buckling accompanied by a significantly large out-of-plane deflection. The computational efficiency of the conventional finite element based full-order method is not satisfactory for nonlinear buckling problems of the structure. In this work, the skin panels on the upper surface of the wing butt box are selected using a sub-modeling technique based on the nonlinear structural analysis. A reduced-order method is proposed to trace the geometrically nonlinear response of the single and double-curved skin panels in a stepwise manner. A predictor-corrector strategy is developed using the Koiter-perturbation-theory based reduced-order model and Newton iterations. The high-efficiency of the proposed method is validated by comparing the number of path-following steps and iterations with the full-order method. A fairly large step size is achieved to significantly reduce the computational cost in a nonlinear buckling analysis. The influence of the number of closely-spaced modes on the numerical accuracy and efficiency of the proposed reduced-order method is also studied. Different boundary condition, location, and thickness of the wing-upper-skin panel, are considered to further demonstrate the favorable performance of the proposed method. • Nonlinear buckling analysis is applied to skin panels with single and double-curved shapes on the wing upper surface. • A reduced-order method is adopted to trace geometrically nonlinear responses in predictor-corrector based stepwise manner. • Influence of the number of closely-spaced modes on numerical accuracy and efficiency of the proposed method is investigated. • Numerical accuracy and high-efficiency of the proposed method are validated for skin panels con- sidering various parameters. [ABSTRACT FROM AUTHOR]

The expansion of lattice-structured tubular stent causes scaffold foreshortening and artery migration during implantation. Based on stent foreshortening attitudes, studies were carried out on hybrid lattices considered Zero Poisson’s Ratio (ZPR) behaviour of arrow, auxetic, and honeycomb unit cell combinations. This paper investigates the energy performance of four ZPR tubular structures inspired by hybrid stent shapes under axial and oblique impact. At the beginning of the workflow of the study, the buckling control of tubular structures was performed using the numerical model. The compression test was performed by 3D printing of the ZPR structure, which was verified to remain uniform under axial loading. The results show that hybrid (H) tubular structures that include ZPR unit cells with different configurations have higher energy absorption and higher crushing force efficiency (CFE) under oblique impact. When the oblique angle is increased, all ZPR tubular structures are unstable from 20 to 40 mm deformation distances due to moving plate compression. H1 has a better CFE value than the other two ZPR configurations when crushed under oblique load. Furthermore, ZPR tubular structures have great advantages for axial loads without buckling behaviour. [ABSTRACT FROM AUTHOR]

This study is based on a theory for analyzing non-uniform torsion in thin-walled beams made of homogeneous elastic material with arbitrary cross-sections by incorporating the effect of the shear deformation of a cross-section. Utilizing the Finite Element Method (FEM), the proposed numerical approach addresses non-uniform torsion by breaking down a 3D analysis into 2D cross-sectional and 1D modeling components. Initially, the geometric constants of the cross-section were computed using a 9-node isoparametric element in 2D FEM. Subsequently, a 1D FEM employing a linear isoparametric element calculated the twist angle, torsion warping parameters, and stress results. The stress field was determined through a local analysis of the 2D cross-section. Notably, the 2D FEM component aligns with contemporary trends in commercial software, thereby bolstering the potential and practical applicability of the proposed numerical approach. Its verification and validation through numerical analyses using MATLAB underscore the efficacy and reliability of the method in analyzing non-uniform torsion behavior in structural design, particularly under diverse boundary conditions. [ABSTRACT FROM AUTHOR]

Here, an analytical form Navier solution for higher-order micropolar theory of cylindrical shell was developed based on the CUF approach. The cases of complete linear expansion and model based on Timoshenko-Mindlin shear deformation hypothesis are considered in detail. The two-dimensional system of differential equations obtained here using the principle of virtual displacements for the theory of micropolar elastic cylindrical shell of a higher order is solved here for the case of freely supported cylindrical shell using the Navier variable separation method. Some numerical examples were performed and the influence of the rotational field, as well as the micropolar couple stress on the stress–strain state, was analyzed. The equations presented here can be used for the stress–strain calculation and for thin-walled structures modeling in macro-, micro-, and nanoscale, with considering effects of micropolar couple stress and rotation. [ABSTRACT FROM AUTHOR]

A curved non-isoparametric Reissner–Mindlin shell element is developed for analyzing thin-walled structures. The standard kinematic description of the element requires the calculation of the director vector. To address this demand accurately, similar to isogeometric analysis (IGA), the geometry is defined by utilization of the non-uniform rational B-splines (NURBS) imported directly from computer-aided design (CAD) files. Then, shape functions of the Legendre spectral element method (SEM) are used to interpolate the displacements. Consequently, the shell director vector and Jacobian of the transformation are calculated properly according to the presented formulation. On the other hand, in Legendre SEM combined with Gauss–Lobatto–Legendre quadrature, the integration points and the element nodes coincide. Thus, the easily computable local coordinate systems at the integration points can be used directly as nodal basis systems. A separate calculation of nodal basis systems at control points, which is the source of either complexity or error in IGA shells, is not required. Given the condition number of the stiffness matrix in the developed method, super high-order elements can also be used. Very high order p-refined elements are used in addition to h-refinement of the mesh to show the capability of higher order elements to analyze problems without mesh refinement. The validity and convergence rate of the method are investigated and verified through various cases of h- and p-refinement in challenging obstacle course problems. [ABSTRACT FROM AUTHOR]

To detect damage in mechanical structures, acoustic emission (AE) inspection is considered as a powerful tool. Generally, the classical acoustic emission detection method uses a sparse sensor array to identify damage and its location. It often depends on a pre-defined wave velocity and it is difficult to yield a high localization accuracy for complicated structures using this method. In this paper, the passive guided wave phased array method, a dense sensor array method, is studied, aiming to obtain better AE localization accuracy in aluminum thin plates. Specifically, the proposed method uses a cross-shaped phased array enhanced with four additional far-end sensors for AE source localization. The proposed two-step method first calculates the real-time velocity and the polar angle of the AE source using the phased array algorithm, and then solves the location of the AE source with the additional far-end sensor. Both numerical and physical experiments on an aluminum flat panel are carried out to validate the proposed method. It is found that using the cross-shaped guided wave phased array method with enhanced far-end sensors can localize the coordinates of the AE source accurately without knowing the wave velocity in advance. The proposed method is also extended to a stiffened thin-walled structure with high localization accuracy, which validates its AE source localization ability for complicated structures. Finally, the influences of cross-shaped phased array element number and the time window length on the proposed method are discussed in detail. [ABSTRACT FROM AUTHOR]

High thin-walled cold-formed steel purlins of the Z cross section are important elements of large-span steel structures in the construction industry. The present numerical study uses the finite element method to analyse the 300 mm and 350 mm high Z cross sections in-depth. The prepared numerical models are verified and validated at several levels with experiments that have been previously published. Significant agreement between the numerical models and the experimental results regarding Mises stress, proportional strain, failure mode, and force-deformation diagram have been obtained. With the verification, the presented procedure and partial findings can be applied to other similar problems. The results can be used to help research and corporate groups optimise the structural design of cold-formed thin-walled steel structures. [ABSTRACT FROM AUTHOR]

This research focuses on investigating the buckling strength of thin-walled composite structures featuring various shapes of holes, laminates, and composite materials. A parametric study is conducted to optimize and identify the most suitable combination of material and structural parameters, ensuring the resilience of structure under both mechanical and thermal loads. Initially, a numerical approach employing the finite element method is used to design the C-section thin-walled composite structure. Later, various structural and material parameters like spacing ratio, opening ratio, hole shape, fiber orientation, and laminate sequence are systematically varied. Subsequently, simulation data from numerous cases are utilized to identify the best parameter combination using machine learning algorithms. Various ML techniques such as linear regression, lasso regression, decision tree, random forest, and gradient boosting are employed to assess their accuracy in comparison with finite element results. As a result, the simulation model showcases the variation in critical buckling load when altering the structural and material properties. Additionally, the machine learning models successfully predict the optimal critical buckling load under mechanical and thermal loading conditions. In summary, this paper delves into the study of the stability of C-section thin-walled composite structures with holes under mechanical and thermal loading conditions using finite element analysis and machine learning studies. [ABSTRACT FROM AUTHOR]

In order to study the influence of modular filled and composite material forms on the axial crushing and energy absorption properties of structures, modular filled composite structures were constructed, and innovatively applied to the inner side of double-hat beam (DHB) structures in automobiles. The modular filled structures comprise hexagonal, quadrilateral, and triangular sections. By analyzing the collision performance of modular filled DHB structures, significant enhancements were observed in both the sectional characteristics and the specific Mean Crushing Force of modular filled DHBs compared to the conventional double-hat beam structure. These advancements notably improved the plastic deformation characteristics of the structures. Additionally, dynamic weightlessness experiments were conducted to validate the accuracy of the simulation model. Among the proposed schemes, namely QU-5, HE-5, and TR-5, notable improvements in crashworthiness were identified. Specifically, crashworthiness indicators increased by 32.54%, 78.9%, and 116.53%. Compared with other thin-walled structures, modular filled composite DHBs have advantages in axial crushing and energy absorption. By optimizing layout characteristics, the modular filled structures will achieve significant lightweight and energy absorption performance improvements. This work has clear reference value for automotive engineers and scholars to further explore the axial crash safety, platform modularization, and lightweight design of vehicles. [ABSTRACT FROM AUTHOR]

This article presents an analytical approach for calculating web stiffeners in thin-walled columns. A novel method is introduced, which treats each bending point in the cross-section web as a separate stiffener. The advantages of this calculation method are discussed, highlighting its increased versatility in designing cross-section geometry. The load-bearing strength of axially compressed thin-walled closed cross-section columns, calculated using this method, is compared to analytical calculations based on the Eurocode 3-1-3 methodology and to the finite element method analysis. Calculation results of columns with cross-sections including shallow web stiffeners were up to 9.22% less conservative when compared to the Eurocode 3-1-3 methodology. The results demonstrate great compliance of the proposed method for column crosssections with deep stiffeners. Finite element method (FEM) analysis was performed to verify the calculated load bearing strengths of the columns according to both calculation methodologies. FEM analysis confirmed the reliance of the calculated results and showed, that the load bearing strengths calculated using the newly presented methodology were ranging from 88.77% to 97.86% of load bearing strength calculated using finite element method. These results proved, that the proposed method provides an accurate load bearing strength of thin-walled columns with web stiffeners. [ABSTRACT FROM AUTHOR]

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Cold-formed steel channel (CFSC) sections have gained widespread adoption in building construction due to their advantageous properties, including superior energy efficiency, expedited construction timelines, environmental sustainability, material efficiency, and ease of transportation. This study presents a numerical investigation into the axial compressive behavior of CFSC section columns. A rigorously developed finite element model for CFSC sections was validated against existing experimental data from the literature. Upon validation, the model was employed for an extensive parametric analysis encompassing a dataset of 208 CFSC members. Furthermore, the efficacy of the design methodologies outlined in the AISI Specification and AS/NZS Standard were evaluated by comparing the axial load capacities obtained from the numerically generated data with the results of four previously conducted experimental tests. The findings reveal that the codified design equations, based on nominal compressive resistances determined using the current direct strength method, exhibit a conservative bias. On average, these equations underestimate the actual load capacities of CFSC section columns by approximately 11.5%. Additionally, this investigation explores the influence of eccentricity, cross-sectional dimensions, and the point-of-load application on the axial load capacity of CFSC columns. The results demonstrate that a decrease in section thickness, an increase in column length, and a higher degree of eccentricity significantly reduce the axial capacity of CFSC columns. [ABSTRACT FROM AUTHOR]

The implosion of underwater composite structures is a critical and complex engineering problem, necessitating high-strength, lightweight, and corrosion-resistant materials for deep-sea applications. This manuscript reviews the intricate failure mechanisms of composite structures, focusing on cylindrical structures under extreme underwater conditions. The recent Titan submersible implosion serves as a case study, highlighting the significance of rigorous design considerations. Key topics include material degradation, buckling instability, and material failure, with a detailed analysis of composite layup optimization and manufacturing processes such as filament winding and roll wrapping. The manuscript underscores the need for comprehensive testing, advanced simulation techniques, and monitoring system integration to ensure the safety and effectiveness of composite pressure hulls. Future research should focus on developing more accurate failure models, optimizing manufacturing processes, and enhancing material properties through innovations in composite science to realize the full potential of composite materials in deep-sea applications. [ABSTRACT FROM AUTHOR]

The study presented the results of model experimental investigations on box structures made using additive manufacturing. The examined models had walls with reinforcements in the form of corrugations. An experiment was also conducted using a reference model without stiffeners. The aim of the study was to determine the influence of corrugation geometry on the shape and magnitude of structure deformations, as well as on the level of critical loads. The experiments were conducted using a dedicated research stand. Nonlinear numerical analyses of selected structure variations were also carried out using finite element method-based software. A comparison of the maximum displacement values obtained by experimental and numerical methods was made. [ABSTRACT FROM AUTHOR]

Thin-walled structures that serve as energy absorbers are widely used in the automotive industry, and it is well-known that they deform in a specific way under dynamic loading, forming plastic hinges along the yield line. The dynamic impact of these structures causes various phenomena that affect the formation of folds and, consequently, the dynamic response of the structure. The force-shortening curve, which is based on the unified crush efficiency indicators, is a key factor in determining the dynamic response of the structure. While there have been many studies on energy absorbers under static or quasi-static loading conditions, the effect of changing kinetic energy components (mass and velocity) on the obtained crush efficiency indicators is not as well understood. This article presents the results of experimental tests and nonlinear numerical simulations for eleven different initial conditions of the crashworthiness analysis. The tests showed a significant effect of changing the velocity and mass of the striker on the results obtained. Additionally, the nonlinear effect of the change in the velocity of the tup with respect to the peak force and total efficiency was demonstrated.

When a car crash occurs, the probability that the collision will be oblique and not entirely frontal is high. In this way, the current article evaluates by a finite element analysis, the crashworthiness performance of multicell structures subjected to oblique loads. In this sense, five multicell structures manufactured with 6063-T5 aluminum alloy were designed and evaluated by an oblique compression test. During the analysis, special emphasis was placed on determining the effect of the cross-section and the angle of incidence of the load (θ) on the energy absorption of the structures. For this purpose, values of θ equal to 0°,5°,10° and 15° were analyzed. To guarantee a correct comparison between tubes, all the structures had the same mass equal to 0.80 kg. Then, adjustments to the thickness were realized. In all cases, the most important indicators of impact resistance such as energy absorption (Ea), crushing force efficiency (CFE), and mean force (Pm) were calculated. According to the results, the angle of incidence of the load defined the plastic deformation mode of the structure. In this sense, a decrease in the Pmax and Pm up to 47.75% was observed as the θ increased. Lastly, at the end of the study, the MC-02 profile presented in average the best CFE value at different loading angles equal to 0.74. Thus, this structure could be considered as baseline among engineers and designers for the design of structures subjected to bending loads.

Inspired by the origami process, a multicellular tube formed by origami folding based on polygons was designed. First, the accuracy of the finite-element model was verified by experiments; then, under the conditions of the same wall thickness, mass, and energy absorption, comparative studies were carried out between multicellular tubes based on polygonal origami folding (MTPOFs), hollow tubes (HTs), and multicellular tubes (MTs). The results showed that regardless of the same wall thickness or the same mass and energy absorption conditions, MTPOFs have advantages over corresponding MTs and HTs. The crushing force efficiency and specific energy absorption of the square MTPOF were 131.45% and 193.57% higher than those of the square HT with the same wall thickness, respectively. Compared with the hexagonal HT, the crushing force efficiency and specific energy absorption of the hexagonal MTPOF increased by 99.02% and 125.01%, respectively. Under the same energy absorption, the crushing force efficiency of the square MTPOF improved by 78.78% and the specific energy absorption improved by 42.05% compared with the square HT. Ultimately, an investigation was conducted into the energy absorption of the structure concerning variations in wall thickness and the ratio of side length to height H/a. As a result, deformation mode diagrams corresponding to different H/a values were obtained. [ABSTRACT FROM AUTHOR]

For unidirectional laminates, four properties are required for mechanical characterization regarding the laminae elastic response: the longitudinal elastic modulus, the transverse elastic modulus, the in-plane shear modulus, and the in-plane Poisson's ratio. Two approaches are usually followed to obtain these properties: an experimental program, which is costly and time-consuming, or micromechanical modeling, which is associated with many uncertainties. The trace theory has been widely explored for carbon fiber-reinforced polymers as an alternative option, where only one independent property is necessary and the others are obtained using a normalized relation with the trace of the stiffness matrix. Considering the wide application of glass fiber-reinforced polymers (GFRPs) in civil structures, an extension of the trace theory was developed by combining micromechanics and machine learning. First, a data set was generated using the asymptotic homogenization for the usual properties ranges of glass fibers and polymeric matrices. Next, the decision trees algorithm was implemented to evaluate the normalized properties variation according to the trace. Based on the results of the training procedure, linear equations were obtained for the normalized properties. The proposed equations were validated by comparing the estimations of the normalized properties with a set of 17 experimental data compiled from the literature, indicating that the average errors range between 3% and 13%. Once the proposed equations were validated, the novel theory was applied to analyze the buckling load of thin-walled structures, where square and channel profiles with different stacking sequences were evaluated. Only the longitudinal elastic modulus was used as input, while the other properties were computed using the trace relations. The properties computed analytically were applied in a finite-element model to calculate the buckling loads, resulting in average errors of this hybrid approach smaller than 10% for both profiles. [ABSTRACT FROM AUTHOR]

The study concerns the comparative analysis of selected solutions of thin-walled structures subjected to constrained torsion, representing the simulation of wing areas weakened by large cutouts. The chosen variants of stiffening were based on the concept of so-called "Misztal torsion box", used in the wing of the PZL-37 aircraft. A series of numerical analyses were conducted, aiming to compare selected variants of structures with reinforcements and a reference structure based on a traditional design scheme. The calculations were performed using software based on the finite element method. An analysis of the stress and displacement distribution of the examined structure was conducted, and the results demonstrating the advantages of the proposed structural solution were presented.

In order to explore the forming mechanism of direct energy deposition of magnesium-lithium alloy wire with high lithium content, this study introduces a novel approach utilizing Cold Metal Transfer Wire Arc Additive Manufacturing (CMT-WAAM) to successfully fabricate thin-walled structures of LA103Z Mg–Li alloy. A comprehensive comparison was conducted to evaluate the microstructure and mechanical properties of different regions on CMT-WAAM samples, in addition to cast and rolled samples. The microstructure of CMT-WAAM samples is mainly composed of β-Li phase and fine needle shaped α-Mg phase, exhibiting a notable divergence from the microstructure observed in cast and rolled samples. It is noteworthy that the mechanical properties along the deposition direction exhibited significant variability in CMT-WAAM samples, but no significant anisotropy is discerned in the mechanical properties along the deposition and scanning directions. The discrepancies in mechanical properties across different regions are predominantly attributed to variations in grain size, and the size and proportion of the α-Mg phase and secondary phases, which are related to the low heat input and high cooling rate of the CMT-WAAM process. The mean tensile strength of CMT-WAAM samples is 159.5 MPa, marking a respective increase of 30.7% and 13.9% compared to cast and rolled samples. These findings underscore the outstanding strength of CMT-WAAM samples compared to conventionally formed samples. This study provides novel insights into additive manufacturing of dual-phase Mg–Li alloys for large-scale complex structures.

Large oil and gas storage tanks serve as crucial industrial energy infrastructures, which are usually thin-walled steel structures with large volumes and light weights, and they are sensitive to wind loads. Under the influence of strong winds or typhoons, large oil and gas storage tanks may suffer wind-induced damage, resulting in the leakage of gas or liquid inside the tanks, posing hazards to the ecological environment and public safety. Therefore, it is of great theoretical and engineering significance to research the wind resistance of large oil and gas storage tanks. This paper provides a comprehensive review of key issues in wind resistance for large oil and gas storage tanks, including characteristics of flow around circular cylinders, wind effects on structures with circular cross-sections, near-surface wind field characteristics, wind effects on large oil and gas storage tanks, wind-induced interference effects, structural dynamic characteristics, wind loads and wind-induced response calculations, multiple load effects, and wind-induced vibration control. The deficiencies of current research are summarized. The prospects for research on the design theory and safety assurance of large oil and gas storage tanks are presented through various methods, including field measurements of near-surface wind fields and wind effects, wind tunnel tests utilizing aeroelastic models, numerical simulations involving fluid–solid coupling, theoretical analysis, and machine learning. [ABSTRACT FROM AUTHOR]

AbstractThe current research presents a dynamically coupled mathematical model considering the energy method and employing the classical Ritz-approximation method for a thin-walled anisotropic tapered rotating box beam. The novelty of this work lies in presenting the effect of circumferentially uniform stiffness (CUS) ply layup to investigate the reverberations of not considering bending-shear couplings toward vibration behavior. The current model is formulated by considering transverse shear and cross-sectional warping of order primary and secondary. The repercussions of not including non-classical effects like Coriolis-force, centrifugal-acceleration and warping, inertial-warping is explored. Mode switching arising for change in geometry and centrifugal stiffening is presented for various ply angles and rotational speeds. [ABSTRACT FROM AUTHOR]

The rapid development of new energy vehicles demands significant improvements in connector structures and performance standards. Wire harness connectors, crucial for linking various electrical components, face challenges due to their small size and thin-walled structure, which can lead to dimensional shrinkage and warping during injection molding. To address these issues, this study optimizes the injection molding process by fine-tuning parameters such as melt temperature, mold temperature, injection time, holding pressure/time, and cooling time. By integrating the Taguchi method with grey relational analysis, the study enhances the molding process for thin-walled composite connectors. This combined approach provides a comprehensive framework for optimizing multiple quality objectives and improving the overall performance of injection-molded composite components. [ABSTRACT FROM AUTHOR]

The stiffened plate is one type of representative thin-walled structure consisting of plates reinforced by varying stiffeners to strengthen its resistance to buckling deformation. However, the mechanism by which stiffeners could efficiently improve the buckling resistance of such structures has not been well reported. Therefore, to investigate the mechanism and predict buckling behavior of the structures accurately, a refined Reddy-type global-local stiffened plate model (RGLS) is established firstly, which can fulfill continuous condition of in-plane displacement and transverse shear stress among the adjacent layers between the plate and stiffeners. In conjunction with the established model, a refined triangular element which can accommodate the continuous condition of transverse shear stresses at the interface between the plate and the stiffeners is constructed. Subsequently, on the basis of the unidirectional stiffened sandwich structures, the symmetric grid-stiffened sandwich structures are proposed. The buckling behavior of grid-stiffened structures is further explored by the present element. A full experimental study and a system of numerical examples have been performed to assess the reliability of the established elements. These examples demonstrate that the buckling loads could be captured by the developed element with high computational efficiency and accuracy. However, the models will significantly overrate buckling loads of the stiffened sandwich structures without considering the continuum condition of the transverse stresses at the plate-stiffener interface. [ABSTRACT FROM AUTHOR]

The use of additive manufacturing to rapidly test and evaluate solutions to engineering problems has been demonstrated. Selective laser sintering (SLS) is a subset of additive manufacturing that is particularly well suited to producing structural thin wall models and end use parts which can improve the ability to prototype and manufacture certain designs at a substantially lower cost and time compared to current methods. However, a more comprehensive understanding of the material properties of these parts is warranted. The presented research investigates the influence of print orientation and sample thickness on the material properties of printed SLS parts. This novel work involves holding a hatch pattern constant across SLS prints using polyamide 12 material to isolate the anisotropic effects of orientation and thickness. An evaluation of ultimate tensile strength, modulus of elasticity, strain at failure, yield strength, and Poisson's ratio, and scanning electron microscope fractography are conducted. Transverse strain and Poisson's ratio are a key aspect that provide insight into the feasibility of building numerical orthotropic models. These data are used to calculate the degree of anisotropy due to both thickness and orientation. The results support the future use of SLS printing and modeling of thin-walled structures, such as scaled structural ship modeling. The presented data provide guidance on the impact of print orientation and thickness that will aid in manufacturing structural parts with intentionally tuned material properties. [ABSTRACT FROM AUTHOR]

The acoustic black hole (ABH) structure exhibits remarkable energy focalization above a given cut-on frequency, offering potential for broadband vibration suppression in structures. However, its energy focusing properties diminish significantly below this cut-on frequency. Therefore, it is crucial to enhance the vibration attenuation capabilities of ABH structures within the low frequency range. This study presents a numerical investigation into the impact of thin-walled structures with embedded ABHs and distributed dynamic vibration absorbers (DVAs) on low frequency broadband vibration reduction. Initially, the focusing characteristics of the ABH thin-walled structure is analyzed, aiding in the attached position of DVAs. Furthermore, the influence of the design parameters and attached position of DVA on the broadband damping effect of the structure is explored. The findings indicate that DVAs designed for low frequencies can achieve significant vibration attenuation across the entire frequency spectrum, including low frequencies, when installed at specific focusing positions. When compared to the position with the maximum vibration response, while the attenuation of the low frequency common amplitude value is slightly reduced, greater vibration attenuation across the entire frequency band is achieved. This research offers valuable insights into optimizing the integration of DVAs with ABHs in thin-walled structures for enhanced broadband vibration attenuation. [ABSTRACT FROM AUTHOR]

• Collaborative Optimization of Simplified Sections of steel/aluminum vehicle body. • Simplified Section was translated into Complex Section under Constraints of Sectional Mechanical Properties. • Optimization method for complex sections controlled by proportional vectors was established. A multi-level matching transformation and optimization design method for complex sections of thin-walled structures in steel/aluminum vehicle body skeleton was proposed. The problems of lengthy body performance numerical analysis and low optimization efficiency were solved by the rapid collaborative optimization of simplified cross-sections and performance of the body skeleton. A complex cross-sections shape library of thin-walled structures in steel/aluminum body skeleton and formulas for solving section mechanical properties were established, which overcame the difficulty of translating simplified cross-sections of thin-walled structures in steel/aluminum body skeleton to actual complex sections. A precise optimization method for complex cross-sections of thin-walled structure controlled by proportional vectors was established, which solved the defect that it was difficult to precisely control the arbitrary change of complex cross-section shape, and provided a new way for lightweight optimization design of complex cross-sections. The proposed method achieved the rapid collaborative design of steel/aluminum body thin-walled structure with complex cross-sections and body skeleton performance through multi-level progressive cross-section matching transformation and optimization. A body skeleton model with actual complex cross-sections was established, and compared with the initial simplified structure, the weight reduction ratio of the body skeleton was up to 6.9 %, and the performance indicators of the body skeleton fully met the design requirements, which verified the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]