Thin-walled Structures Research Articles

Energy absorption characteristics of corrugated grooves thin-walled structure inspired by nautilus shell biological geometry

Energy absorption characteristics of corrugated grooves thin-walled structure inspired by nautilus shell biological geometry

Experimental Study of Compression Behavior on Monolayer FFF Samples

Additive manufacturing (AM) processes, such as Fused Filament Fabrication (FFF), enable the production of lightweight parts with high stiffness-to-weight ratios, making them highly suitable for a wide range of engineering applications. However, ensuring the mechanical reliability of these components, particularly for load-bearing purposes, requires systematic mechanical testing of well-designed specimens to asses their suitability. While the tensile properties of additively manufactured materials have been extensively studied, the compressive behavior of components produced via AM, particularly those made from thermoplastic materials, remains comparatively underexplored and insufficiently characterized in the existing body of research. Among these materials, polylactic acid (PLA)—a biodegradable thermoplastic derived from renewable resources—has gained prominence in AM applications. Recent studies have investigated the compression properties of PLA in reinforced materials; however, the focus has primarily been on solid, semi-solid, or porous specimens. These investigations largely overlook thin-walled structures, which are integral to weight-saving designs and commonly feature in topology-optimized structures. Understanding the mechanical behavior of monolayers, the fundamental building blocks of most AM components, is essential for accurately predicting the overall performance of multilayer structures. Monolayers represent the smallest, most basic structural elements of AM parts, and their properties directly influence the behavior of the final, more complex assemblies. Establishing a methodology that correlates monolayer properties with those of multilayer components could significantly streamline testing procedures. By performing mechanical tests on monolayers, instead of on more intricate multilayer specimens, manufacturers could reduce testing complexity and cost while accelerating the development process. The current literature reveals a gap in the design and analysis of thin-walled AM specimens, especially monolayers, under compressive loads. Specifically, the design of monolayer or thin-walled AM compression specimens without infill has not been thoroughly explored. This article addresses this gap by investigating the design and testing of AM monolayer compression specimens produced using FFF of PLA. Three distinct specimen geometries are considered—circular, helicoidal, and S-shaped—to evaluate their potential for understanding and predicting the compressive behavior of AM monolayer structures.

Mathematical modeling of the process of nonlinear deformation of thin-walled structures

Objective. The objective is to develop a unified method for solving a general nonlinear boundary value problem associated with discontinuous phenomena, which allows identifying all the characteristic features of the behavior of thin-walled systems under load. The issues of nonlinear deformation, loss of stability of the initial equilibrium shape and post-critical behavior are considered using the example of a thin spherical shell. Method. The problem is solved by numerical and analytical methods, representing a set of methods of catastrophe theory and the finite difference method of increased accuracy. The main attention is paid to the mathematical aspects of the phenomena under consideration. Result. The parameters of the stressstrain state of subcritical, critical and postcritical deformation are determined using a spherical shell as an example. The relationships between the limit and bifurcation values of the load parameters are obtained, allowing us to determine the group of the limit state of the achieved level of the stress-strain state of the structure. Conclusion. The solution of the general problem allows us to obtain complete and necessary information to determine the degree of danger of the states of structures and ensure their reliability.

Analytical and numerical investigations of metal square origami foam-filled tube under axial compression

It is widely known that thin-walled structures are expected for numerous engineering devices, due to lightweight, high specific strength, and excellent energy absorption capacity. Thus, the new high-efficiency energy absorbing (EA) device is the eternal pursuit goal of designers. A novel high-efficiency energy-absorbing device of the metal square origami foam-filled tube (MSOFT) under axial compression is designed in this article, and axial crushing of the MSOFT is investigated analytically and numerically. An analytical model for axial crushing of MSOFT is established based on the conservation of energy and the hyper-folded unit theory, considering the energy absorbed by the deformation of metal origami tube, foam compression, and the interaction between foam and origami tube. Then, the finite element (FE) simulation of MSOFTs under axial compression are conducted by Abaqus/Explicit software, and found that theoretical results are in good consistency with the FE results. Then, the influences of yield strength, wall thickness, height and cross-section width of the tube, and foam strength of MSOFT under axial compression are discussed, and found that the force and energy increases when the above parameters increase. Finally, the mean crushing force (MCF) and the crushing force efficiency (CFE) among MSOFT, origami tube and square tube are compared. Compare with the origami tube and square tube, the MCF of MSOFT increases by 40.8–106.9% and 12.1–49.8%, and the CFE of MSOFT increases by 101.2–266.3% and 1.1–12.4%. It is indicated that for a wide range of geometric and material parameters the MSOFT exhibits predictable and stable collapse behavior.

Skanowanie laserowe w diagnostyce imperfekcji geometrycznych hiperboloidalnych chłodni kominowych

Hyperboloid cooling towers are distinctive tower structures designed to cool industrial waters by discharging their heat into the ambient air. Geometric imperfections of the hyperboloid cooling tower shell are the main, easily measurable symptom of structural strain and a significant factor in the development of safety hazards and failures of these thin-walled shell structures. This article presents an analysis of the use of a ToF and a phase laser scanner in the diagnosis of geometric imperfections of the reinforced concrete cooling tower shell. The reliability of TLS data in mapping the actual shape of the hyperboloid structure was confirmed on the basis of precise reflectorless tachymetry, which serves as reference data. Geometric imperfections of the hyperboloid cooling tower shell were determined by referring the TLS observation sets to a modified model hyperboloid, adjusted to the external surface by taking into account the actual, variable distribution of the shell thickness. Statistically confirmed compliance of the shell geometry analysis results, carried out on the basis of data obtained with two scanners with different parameters, showed no influence of the distance measurement system used in the scanning instrument on the effectiveness of detection of geometric imperfections of the hyperboloid structure. The results of the analyses of the shape of the cooling tower shell were consistent with the information on the geometric state of the structure, collected in the company archive. The imperfection maps generated on the basis of data obtained with the phase and the ToF pulse laser scanner clearly confirmed the deformations of the critical areas of the structure, which do not pose a real threat to the stability of the facility.

Static/quasi-static thermomechanical analysis of 3D thin-walled beam structures based on CUF considering radiation dissipation condition

Thin-walled structures are widely applied in spacecraft as structural components due to their lightweight property. Extreme thermal environment in space may cause highly unfavorable thermal responses in thin-walled structures. Therefore, accurately predicting the thermal-coupling responses of thin-walled structures is of great engineering significance. In order to avoid the disadvantages of 3D finite element model caused by an abundance of computational degrees of freedom, the present paper proposes a thermo-mechanical coupling model based on Carrera Unified Formulation (CUF) for the static and quasi-static thermal response of space thin-walled structures. The longitudinal direction of the structures is discretized by one-dimensional linear and cubic finite elements (B2 and B4), whereas Lagrange expansion functions are used for the description of temperature fields and displacement fields within the cross-section. The governing differential equations of thermal-coupling problems are derived in a unified form according to the principle of virtual displacement and the weighted residual method. In order to demonstrate the accuracy of the numerical results, a convergence analysis is conducted on both beam elements and expansion forms. The results reveal that piece-wise quadratic beam theories approximated with B4 elements are accurate enough for the prediction of thermally-induced displacements, while the high-order cubic cross-sectional expansion is required for the description of stresses. Finally, influences of factors like angle of solar radiation, local shadows, emissivity and thermal conductivity on static and quasi-static displacement distributions are discussed. This research may pave a high-efficiency computational method for solving static/quasi-static thermally induced response of space thin-walled structures.

Assembly deviation analysis for large closed thin-walled structures with geometrical deviation and jointed deformation

The combined effect of geometrical deviations and jointed deformation in the assembly process are essential for the assembly accuracy of large closed thin-walled cylindrical structures, such as roundness and flatness of the edge, which determines the further assembly between two cylindrical structures. In this paper, a new geometrical deviation propagation model is proposed for large closed cylindrical structures with high local stiffness, in which the geometrical deviation, jointed deformation, and coordinated deformation in the closed assembly process are considered simultaneously. The constraint conditions of the dimensional deviations and shape deviations are derived by small displacement torsor. A virtual deviation feature is developed to describe the equivalent deviation caused by jointed deformation of two cylindrical parts. The correlation of the structural stiffness between unenclosed structure and closed cylindrical structure are established and the geometrical accuracy is obtained by the deformation coordinated conditions. The quantitative index of deviation contribution between parts and assembly is developed based on the deviation propagation model. The influence of geometrical deviation and jointed deformation on the geometric accuracy of assembled structure is revealed. The new deviation propagation model is verified by the experimental data, which may be used for prediction and control of assembly deviation for large closed thin-walled cylindrical structures with high local stiffness.

Crashworthiness analysis of a novel transverse double-gradient hierarchical multi-cellular square tube

This paper presents an innovative design approach for a square multicellular tube, incorporating the concepts of gradient hierarchical design and tree fractals. The design involves simultaneous development of the inner and outer parts of the tube with gradient hierarchies, resulting in a transverse double gradient hierarchical multicellular tube with right-angle fractal (TDGHMST). Ten different cross-section schemes are proposed, and a finite element model is developed using Abaqus/Explicit to analyze the energy absorption characteristics under axial impact. Comparing the crashworthiness indexes of different orders of TDGHMST structures, the findings reveal that third-order double-gradient hierarchical multicellular tubes exhibit significantly higher energy absorption capacity and crushing force efficiency than lower-order multicellular tubes. Moreover, the crashworthiness performance of the third-order tubes is substantially improved, regardless of the wall thickness or mass condition. The paper also investigates the effect of the inner tube edge length (L 1) variation on the structural crashworthiness. In addition, analyses of the geometrical parameters, including wall thickness (t) and aspect ratio (H/L), are conducted, demonstrating their significant impact on the crashworthiness of the square gradient-layered multicellular tube. Finally, through comparative studies with other multicellular tubes, the superior energy absorption performance of the proposed dual-gradient hierarchical multicellular tube is verified. These research results provide valuable guidance for the practical application of thin-walled structures and the optimal design of crashworthiness.

Development of Criterion for Long-Term Failure Due to Creep of Thin-Walled Layered Structures

Development of Criterion for Long-Term Failure Due to Creep of Thin-Walled Layered Structures

High-efficiency analysis of electromagnetic-thermal effects for absorbing honeycomb based on transformation optics.

Wave-absorbing honeycombs have garnered widespread attention due to their high-efficiency absorption, ultra-wideband absorption, lightweight nature, and high load-carrying capacity. However, as electromagnetic radiation power increases, the temperature of the absorbing honeycomb increases rapidly, even leading to burning. Therefore, it is significant to possess an efficient and accurate assessment of the thermal effects of absorbing honeycombs under electromagnetic radiation. However, the complex thin-walled structure of the honeycomb increases computational complexity, resulting in time-consuming, resource-intensive, and occasionally unsolvable actions. To address this issue, we implement transformation optics to expand the thin-walled structure and reconstruct the transformed electromagnetic and thermal property parameters. The transformed electromagnetic-thermal coupling simulation results were highly consistent with the actual model. Specially, the mesh count dropped from 272,717 to 17,621, the simulation time decreased from 15,792s to 242s, and the efficiency was improved by 65 times. The proposed methodology overcomes analysis difficulties on multi-scale complex structures, making it possible to analyze the honeycomb structures that traditional methods cannot handle.

Mechanisms of interlayer friction in low-dimensional homogeneous thin-wall shell structures and its strain effect.

Due to the multi-factor coupling effect, the rule of interlayer friction in low-dimensional homogeneous thin-wall shell structures is still unclear. Double walled carbon nanotubes (DWCNTs) having a typical low-dimensional homogeneous thin-wall shell structure are selected for this study. The interlayer friction of numerous chiral DWCNTs is investigated using molecular dynamics simulations to systematically analyze and understand the coupling mechanisms of various factors in interlayer friction. To eliminate the influence of the edge effect, a high-speed pure rotation model is used. The results demonstrate that DWCNTs with varying mismatch angle, interlayer distance, and interfacial radius exhibit distinct interlayer frictions and strain effects, due to the differences in interlayer interaction, atomic vibrational amplitudes, and lattice periods. Theoretical analysis is conducted on the interlayer friction and its strain effect based on the theoretical model. Based on phonon spectrum analysis, the vibrational modes and energy dissipation of DWCNTs with different chiral combinations under various strains are demonstrated. Based on the analysis, physical insight into the variation in friction forces is provided. The findings of this work deepen the understanding of the interlayer friction and strain mechanism and provide a theoretical basis for further exploitation of the strain effect to realize the regulation of nanoelectromechanical devices.

Corrigendum to “Strength degradation and damage mechanism of TA1 titanium alloy clinched joints under fatigue loading” [Thin–Walled Structures 202 (2024) 112125

Corrigendum to “Strength degradation and damage mechanism of TA1 titanium alloy clinched joints under fatigue loading” [Thin–Walled Structures 202 (2024) 112125

Implosion collapse of externally pressurized steel/CFRP/titanium cylindrical shells with a hybrid sandwich thin-walled structure

Implosion collapse of externally pressurized steel/CFRP/titanium cylindrical shells with a hybrid sandwich thin-walled structure

Investigation on energy absorption characteristics of thin-walled structures fabricated by bound metal deposition without using debinding chemical reagents

Investigation on energy absorption characteristics of thin-walled structures fabricated by bound metal deposition without using debinding chemical reagents

A novel design strategy to enhance buckling resistance of thin-walled single-cell lattice structures via topology optimisation

ABSTRACT Lattice structures with thin walls or members are susceptible to instability due to their limited buckling strength. We propose a design methodology that utilises topology optimisation techniques to create lattice structure members with improved buckling resistance, demonstrated here on a single cell of a thin-walled square honeycomb lattice. We utilise the buckling mode of the single cell as a reference to inform the design of modified lattice structure members via optimisation, while ensuring the weight and stiffness of the structure remain unchanged. We apply a 2D topology optimisation method with the objective of maximising buckling load factors, while simultaneously enforcing constraints on stiffness and volume fraction within the optimisation domain. A family of designs is created via a parametric study, considering optimisation parameters like the thickness of the buckling member and the active domain. Designing and fabricating these structures also consider additive manufacturing constraints, such as minimal feature size and overhang. Experimental analysis of fabricated structures reveals a remarkable 70% increase in buckling strength without altering stiffness or weight. Numerical simulations corroborate these findings, with a discrepancy of less than 10%. This methodology shows the potential to enhance buckling resistance of thin-walled lattices in various lattice types while maintaining base cell stiffness.

Numerical investigation on energy absorption characteristics and damage modes of biomimetic thin-walled structures in aircraft

The crashworthiness of aircraft is essential for both airlines and passengers. Creating lightweight protective structures that achieve a balance between weight and impact resistance while also providing excellent cushioning and energy absorption presents a significant challenge for aircraft designers. The desert beetle's exoskeleton demonstrates remarkable strength and toughness, effectively shielding its body from external threats. This study examines the desert beetle's exoskeleton by developing bio-inspired thin-walled models with three distinct bottom structures based on its cross-section. Numerical simulations were used for calculations and model optimization. The research systematically investigates how various design parameters, such as impact angle, number of support plates, and wall thickness, affect energy absorption performance. The findings indicate that increasing the inclination angle notably decreases the energy absorption capacity of the protective structure, while adding more partitions can significantly enhance this capacity. Additionally, changes in wall thickness directly influence the structure's compressive performance. Furthermore, a comparative analysis of the optimized structure's energy absorption characteristics under various conditions is provided. Ultimately, this paper highlights the significance of design optimization for protective structures in micro aerial vehicles and outlines future research directions to better balance performance and practicality.

Research Status and Development of Assembled Lightweight Steel Composite Structures

Prefabricated lightweight steel composite structures are characterized by efficient load-bearing, seismic energy-saving, and eco-friendly attributes, primarily used in low-rise and multi-story buildings, adapting to the development of modern architectural industrialization. This review covers the development process, system composition, and current research status of structural seismic performance for typical prefabricated lightweight steel composite structures, including prefabricated cold-formed thin-walled steel structures, prefabricated lightweight steel-lightweight concrete structures, and prefabricated lightweight steel composite frames - lightweight steel composite shear wall structures. The analysis includes the technical features, standard systems, and current environmental applications of the aforementioned structures, raises several issues in the research of prefabricated lightweight steel composite structures, and provides a research outlook for the future development direction of prefabricated lightweight steel composite structures.

Highly Compressible Micro/Nanofibrous Sponges with Thin-Walled Cavity Structures Enable Low-Frequency Noise Reduction.

Increasing noise pollution has generated a tremendous threat to human health and incurred great economic losses. However, most existing noise-absorbing materials present a significant challenge in achieving lightweight, robust mechanical stability, and efficient low-frequency (<1000 Hz) noise reduction. Herein, we create highly compressible micro/nanofibrous sponges with thin-walled cavity structures for efficient noise reduction through electrospinning and dispersion casting. Manipulating the phase separation driven by solution/water interaction in jets enables formation of fluffy fibrous frameworks, on which the deformation of casting dispersion is controlled to develop thin-walled cavity structures consisting of semiopened cells and entangled networks. The resultant sponges exhibit lightweight characteristics (2.2 mg cm-3) and mechanical robustness, integrated with remarkable low-frequency noise reduction capability (absorption coefficient up to 0.98) benefiting from vibration and viscous friction effects of cavity-structured skeletons. This work may offer new horizons for designing advanced fibrous acoustical materials, inspiring next-generation noise-reducing devices in aerospace and transportation.

A FINITE ELEMENT MODEL FOR CALCULATING A NON-THIN ORTHOTROPIC CYLINDRICAL SHELL, TAKING INTO ACCOUNT THE INDUCED INHOMOGENEITY

The formulation of a model for the deformation and strength calculation of an open cylindrical shell of circular shape rigidly pinched along contour planes formed by generators is considered. The ratios of the geometric parameters of the shell differ significantly from thin-walled structures, to which traditional technical hypotheses could be applied. The formulation of a mathematical model defining the stress-strain states of a thick-walled structure was carried out within the framework of a nonlinear three-dimensional theory. The peculiarity of the developed model was that orthotropic composites were adopted as the structural materials of the shell, the deformation and strength properties of which manifest themselves in different ways in accordance with the types of stress states being realized. The manifestation of such mechanical properties of materials is interpreted as induced heterogeneity, which significantly complicates the methodology for calculating spatial structures. Due to the specified features of the research object, isoparametric finite elements of a three-dimensional tetrahedral shape, the nodes of which had three degrees of freedom, were used to develop a computational model. In order to adequately account for the stiffness properties of orthotropic composites exhibiting induced heterogeneity, the basis of the determining relationships for them was the deformation potential formulated in the normalized stress tensor space associated with the main axes of orthotropy of materials. Due to the nonlinearity of the problem under consideration, the process of solving it was based on the method of variable elasticity parameters. As a result of the implementation of the computational model, comprehensive information was obtained on the stresses, deformations and displacements of the shell, the main of which are presented in the text of the article with the addition of their analysis.

A Study of the Response Surface Methodology and Finite Element Method to Model Aircraft Engine Body Deformations During Hole Drilling.

The aviation industry is still looking for effective manufacturing methods. Currently, the challenge is still the machining of shapes in thin-walled materials. This work focuses on the analysis of the influence of these parameters on deformations during the drilling process of holes in the adapters of aircraft engine body accessories. The drilling process was carried out in the thin-walled superalloy Inconel 718, which is classified as a difficult-to-machine material. During the analyses, experimental studies based on the Response Surface Method (RSM) and finite element method (FEM) calculations were carried out simultaneously. The aim of this work was to analyze the developed mathematical models describing nonlinear relationships between cutting parameters, cutting forces, and deformations of the aircraft engine body characterized by a complex, thin-walled geometric structure. By using the proposed solutions, it is possible to achieve integration between the techniques of conducting research, performing calculations using FEM, and designing the machining. The advantage of this comprehensive approach used in our work is the development of mathematical models that strongly fit the results of the research. The results of analyses and calculations presented in the article and the research methodology used can be applied to industrial conditions.