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• The elastic instability phenomenon in hyperelastic layered materials with the phases exhibiting stiffening behavior is studied • A closed-form expression for the critical stretch of macroscopic instability is derived • An analytical prediction based on Bloch-Floquet analysis for the microscopic instability is exhibited • The critical parameters and transition of instability modes are found to be highly tunable with phase stiffening This paper investigates the elastic instability behavior in soft periodic laminates subjected to finite strains, with a focus on both macroscopic and microscopic instabilities. Considering the deformation-induced phase stiffening, the Gent model with a high bulk-to-shear modulus ratio describes the behavior of incompressible phases. This non-Gaussian statistics-based model captures the non-linear constitutive results from the limited extensibility of polymeric molecular chains. This paper derives an analytical prediction for the onset of macroscopic (or longwave) instability and microscopic instability as functions of material parameters. Moreover, a numerical Bloch-Floquet analysis is imposed on identifying the instability behavior under compression. We consider a wide range of phase combinations and find that the relatively rapid stiffening of the matrix compared to the stiff layer increases the stability of laminates by decreasing the critical stretch ratio. Essentially, properly manipulating the stiffening parameters can produce an absolutely stable region without observed instability. This paper also systematically illustrates the changes in instability and the transition between macro and micro instability in fully Gent laminates, which show higher stability than fully neo-Hookean laminates with larger critical stretch ratios. The critical characteristics of instabilities, such as critical stretch ratios and critical wavenumbers, can be controlled by the choice of stiffening parameters and other material properties, enlarging the tuning of soft laminates for desired buckling patterns in practical applications. [ABSTRACT FROM AUTHOR]

This paper investigates experimentally and numerically the buckling behavior of three-layered cross-laminated timber (CLT) panels under in-plane axial compression. The main aim is to assess the panels' ultimate limit load and their typical failure mechanisms. A total of 14 specimens were tested. Seven of them were homogeneous (HO series), entirely made of beech, whereas the others were hybrid (HB series), made of beech (outer layers) and Corsican pine (inner layer). The tests gave evidence of a rather stable column buckling capacity for CLT panels, with evidence of major failure mode due to bending. In some cases, rolling shear and delamination were highlighted as additional failure mechanisms. Finally, further assessment of experimental evidence is provided by extended analytical calculations (based on existing formulations, including the Eurocode 5 approach) and even finite-element (FE) numerical analyses for the examined three-layer CLT compositions. Comparative results are discussed in terms of structural performance, capacity, and weakness of analytical models for CLT solutions. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of an open hole on the stability of a compressed laminated composite plate. The study was carried out in two ways: using experimental tests and numerical analysis. As a result of the experiment, the buckling form and path of the plate were recorded. The form of buckling was determined using the ARAMIS non-contact measurement system. The critical load value was determined from the working path using the approximation method. The experimental results were verified by numerical analysis based on the finite element method. FEM investigations were carried out in terms of a linear eigenproblem analysis. This allowed the bifurcation load and the corresponding buckling form of the numerical model of the plate to be determined. Investigating the effect of the hole in the compressed plate at a critical state showed high agreement between the proposed test methods. No clear effect of the hole size on the buckling of the plate was observed. In contrast, a clear effect of the hole on the critical load value was determined. The maximum decrease in the critical load value was 14%. The same decrease was observed for the stiffness of the post-critical characteristics. It was shown that the [45|−45|90|0]s composite plate had more than three times lower strength compared to [0|−45|45|90]s and [0|90|0|90]s. The novelty of this article is the development of a research methodology based on new interdisciplinary research methods for describing the influence of the central hole on the stability of compressed composite plates. The ABAQUS system was used for the numerical analysis. [ABSTRACT FROM AUTHOR]

We comment on the paper published by Sakata et al., in J. Adv. Compos. Mater., 2018, 27, 35–51, which was in continuation of the previous work by Sakata and Ben in J. Adv. Compos. Mater., 2012, 21, 445–457. Although the experimental section in both works were identical, the reported numerical values of the linear buckling loads differed. In addition, all the specimens were manufactured using an identical process by employing silicone rubber mold and filament winding technique, and outer skin layers and stiffeners consisted of a fixed number of plies. Nonetheless, different shell thicknesses and stiffeners cross-sectional areas were reported for the specimens. Since the buckling behavior of cylindrical shells is highly sensitive to their thickness, the difference in the reported numerical linear buckling loads of the mentioned studies could be due to different thickness values used as inputs for their numerical analyses. In order to address this subject, the present study aimed to provide complete and comprehensive data on the buckling behavior of unstiffened and grid-stiffened cylindrical shells with the same material properties and geometrical dimensions but various thicknesses. The presented results can be used as a benchmark for future studies. [ABSTRACT FROM AUTHOR]

Testing shear-resisting plates in steel connections is one of the most challenging laboratory undertakings in steel construction, as the most common experimental layout design includes simulating the connection with its adjoining members. This significant hindrance gained particular magnitude as the need to test prototypes of topologically optimised shear cover plates became more pressing. Indeed, new code-compliant topology optimisation approaches for steel construction have recently been offered, and physically non-linear analyses have been demonstrated to be vital for assessing these elements. Hence, a rapid and reliable experimental process has become a fundamental necessity. To answer this need, a novel layout is herein proposed, in which topologically optimised and previously numerically examined bolted shear plates of a well-known steel joint were tested. The results allowed for the definition of the material trilinear model for use in subsequent numerical analysis, as well as the validation of the numerical simulation results. The discrepancy between the previously mathematically anticipated and empirically determined ultimate resistance did not exceed 1.7%. [ABSTRACT FROM AUTHOR]

Topologically interlocked materials (TIMs) are an emerging class of architectured materials that each of block is supported by their neighboring blocks without any connector, which is inspired by microstructures observed in nature. Therefore, they showed alluring attributes such as resistance to impact, toughness, high flexibility even when using brittle materials, and high crack propagation resistance. In these structures, the presence of lateral compressive force, applied on peripheral blocks, ensures the integrity and identified properties. Lateral load, however, can adversely affect TIM plates and cause instability, and initiate buckling. In the present study, to focus on the buckling behavior of TIM plates due to the lateral force, a finite element model of TIM plates, made of tetrahedral blocks, was first validated using numerical results available in the literature and then analyzed. In this regard, an appropriate procedure has been presented to simulate the possible instability of these structures. Unlike monolithic plates, geometric parameters of TIM plates are dependent and this makes their parametric study more challenging. Therefore, some case studies have been accomplished to illustrate the effect of diverse parameters. The current study indicates that increasing the assembly plate length and decreasing its thickness causes a reduction of buckling load; nevertheless, it is necessary to mention that the thickness variation is a more impressive factor. [ABSTRACT FROM AUTHOR]

The Finite Strip Method (FSM) was employed to study the buckling behavior of laminated glass fiber-reinforced polymer (GFRP) stiffened plates with different boundary conditions under axial compression. The theoretical formulation was established based on the first-order shear deformation theory (FSDT) for the thin plate and the stiffener. In this formulation, the stiffeners are not required to be placed on the nodal lines. This feature is considered useful in modeling the stiffened plates in which the stiffener elements are placed arbitrarily in complex planforms. Experimental, numerical and analytical studies were conducted to investigate the effects of the plate width-to-thickness ratio, the stiffener thickness-to-width ratio, dimensions, angle, eccentricity, torsional stiffness and geometric configuration of stiffeners on axial buckling capacity. Furthermore, the obtained results of the analytical method were compared with experimental results and ANSYS code to show its accuracy and convergence. The advantages of the present are that number of elements is much less and the mesh refinement process is much more convenient than commercial finite element software and traditional finite element method (FEM). Therefore, time consumed for analysis is less than the codes which work based on the finite element method. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine how the change of glass laminate fibres to flax fibres will affect the stability of thin-walled angle columns. Numerical analyses were conducted by the finite element method. Short L-shaped columns with different configurations of reinforcing fibres and geometric parameters were tested. The axially compressed structureswere simply supported on both ends. The lowest two bifurcation loads and their corresponding eigenmodes were determined. Several configurations of unidirectional fibre arrangement were tested. Moreover, the influence of a flange width change by ±100% and a column length change by ±33% on the bifurcation load of the compressed structure was determined. It was found that glass laminate could be successfully replaced with a bio-laminate with flax fibres. Similar results were obtained for both materials. For the same configuration of fibre arrangement, the flax laminate showed a lower sensitivity to the change in flange width than the glass material. However, the flax laminate column showed a greater sensitivity to changes in length than the glass laminate one. In a follow-up study, selected configurations will be tested experimentally. [ABSTRACT FROM AUTHOR]

In large metal civil constructions (stadium roofs, bridges), slender bars can lose their stability under compression loading. There is a lack in the literature regarding design solutions and methods for increasing the critical buckling force of bars with variable cross-sections. The aim of this research is to present a numerical model with finite elements used for a comparative analysis of increasing the critical force of stability loss in cases of (i) bars with stepwise variation in the cross-sections and (ii) bars with continuous variation in the moment of inertia along the bar axis (parabolic, sinusoidal, triangular, and trapezoidal variation). Considering the large-scale applications in civil engineering, bars that were pin-connected at one end and simple-supported at the other end were analyzed. Firstly, the analytical model was described to compute the critical buckling force for bars with stepwise variation in the cross-sections. Then, a finite element model for a slender bar and the assumptions considered were presented. The results were computed using the MATLAB program based on the numerical model proposed and were validated with the analytical model for stepwise variable cross-sections of the bars. The numerical model was adapted for bars with continuous variation in the moment of inertia along the bar axis. It was shown that, by trapezoidal variation in the second moment of inertia along the axis of a bar, i.e., as buckling occurred in the elastic field, the critical buckling force could be increased by 3.556 times compared to a bar with a constant section. It was shown that there was certain bar with stepwise variation in the cross-section for which the critical buckling force was approximately equal to the one obtained for the bar with sinusoidal variation in the moment of inertia (increased by 3.427 times compared to a bar with a constant section). [ABSTRACT FROM AUTHOR]

In this paper, we propose an archetypal double-winged novel nonlinear oscillator composed of torsional springs and rigid rods which behaves smooth and discontinuous dynamics and a kind of special collision pendulum depending on the varying of a geometrical parameter. The system behaves complicated equilibrium bifurcations with different geometrical states, leading to a series of buckling phenomenon and the loss of uniqueness near the limit points. A 'collision' parameter is introduced to determine the motions near the limit points which causes a discontinuous jump of velocity and exhibits the standard dynamics as an inverted pendulum, even though the mechanic model is rather different from a pendulum. We also distinguish the coexistence of periodic and chaotic motions and also a smooth period 1 located in a small region under the presence of damping and external force using amplitude–frequency analysis and numerical simulations. This research enriches the complicated dynamical behaviors of geometrical nonlinear oscillator and provide a novel structure which is of great potential in vibration isolation engineering. • An archetypal double-winged nonlinear oscillator is proposed. • Discontinuous force and discontinuous motions are formed. • Buckling phenomenon and multiple equilibrium states are found. • Discontinuous singulars are discovered on inverted pendulum system. [ABSTRACT FROM AUTHOR]

Cylindrical shells with corrugation are widely used in deep sea, underground pressure structures, and other fields. It is mainly subjected to uniform and concentrated external pressure. The current research mainly includes circumferentially corrugated shells and longitudinally corrugated shells. These two kinds of corrugations improve the strength of the cylindrical shell but also have some problems such as stress concentration, buckling extension, and so on. To solve these problems, a shell with composite corrugation is proposed and it has the structural characteristics of both circumferential and longitudinal corrugations. In this paper, the numerical analysis method is used to explore the stability of the composite corrugated shell under uniform and concentrated pressures. It is analyzed by Donnell's large deflection equation. In addition, it can reduce the area of damage caused by buckling. The excellent mechanical properties of the composite corrugated shell are proven. The influence of the number of corrugations and "diameter to thickness ratio" on the buckling performance is studied by using the control variate method. It is compared with a cylindrical shell without corrugation with equal volume and weight. The concentrated pressure tests of composite corrugated shells and shells without corrugation are finished. The results show that the curve of "radial compression-reaction load" obtained by the experiment is consistent with the simulation. The ultimate load of the composite corrugated shell is 34.96% higher than the shell without corrugation. The composite corrugation can effectively enhance the compressive strength and stiffness of the cylindrical shell. Composite corrugation can make more material of the shell to be involved in resisting external deformation. This method of increasing material utilization is effective. • The advantages of the composite corrugated shell are verified from mechanical theory, finite element analysis and test. • The influence of local curvature on the buckling performance of cylindrical shell is verified. • Donnell's large deflection equation has been applied and innovated in this paper. [ABSTRACT FROM AUTHOR]

Background: Accurate predictions of thin sheet material springback during forming processes are of great interest in the forming industry. However, thin sheets are susceptible to buckling under shear loading. Objective: The present research aims at improving the so-called Arcan setup for testing thin (1-5 mm) sheet samples with large gauge areas (i.e., width about 21 mm) by introducing anti-buckling devices to mitigate sample buckling. Method: Three monotonic and one cyclic shear tests were carried out on 1 mm thick C60 high carbon steel. Results: The use of the proposed anti-buckling device resulted in the suppression of sample buckling. Numerical analyses of the experiment where buckling was eliminated revealed predominant shear stress states in the gauge area (i.e., stress triaxiality = 0), which highlights minor influences of the anti-buckling device on the sample stress state. Conclusion: To suppress buckling, the use of anti-buckling devices was essential. Moreover, the friction coefficient between the sample and the proposed devices was calibrated ( μ = 0.33 ) in addition to kinematic hardening parameters. [ABSTRACT FROM AUTHOR]

What are the geometrical and mechanical properties ruling bistability of Kresling origami metamaterials? How can we tune the magnitude of their axial-torsional coupling? Complete answers to these compelling questions cannot be found in the scientific literature, as the intertwining between bistability, axial-torsional coupling and an other significant behaviour, namely transverse dilation/contraction, remains mostly uninvestigated. This contribution aims at shedding light on this intertwining, through the use of a discrete model of Kresling origami that takes into account folding resistance. The present study is mostly computational and involves both pre- and post-critical analyses. It is based on displacement controlled tests — shearing and axial shortening/lengthening. Single-storey Kresling origami's are first considered, preliminarly to multiple-storey tubes, where buckling is observed. Several parameters are taken into account such as the number of storeys, stretching and folding stiffnesses, and – for shearing tests – the prescribed displacement direction in the transversal plane. The ultimate goal of the paper is to provide evidence that can be useful in the construction of homogenised continuum models of Kresling origami metamaterials. • We present some numerical simulation concerning metamaterials based on Kresling tube pattern. • Numerical analyses of some selected tests clarifies the mechanical behaviour of metamaterials based on Kresling pattern. • Numerical simulations address the homogenised model of Kresling tubes. [ABSTRACT FROM AUTHOR]

• Deriving the strong-form of the classical sandwich plate with boundary condition under in- plane pre-loading. • Predicting the buckling load of the rectangular plate with boundary condition using vibration correlation technique for the first time. • Using meshless collocation method based on radial function in vibration correlation technique for the first time. • The use of artificial neural network and genetic algorithm in obtaining the optimal geometric parameters for elliptical cutout. • Comparison of critical load and shape of buckling and vibration modes in two numerical methods meshless and finite element with experimental method. The present research was carried out in order to estimate the buckling load of a sandwich plate with a trapezoidal corrugated core with cut-out using three vibration correlation techniques (VCT). The structure investigated in this research is a sandwich plate with a trapezoidal core and an oval cut-out, which is made of thermoplastic polymer using a 3D printer. By using artificial neural network (ANN) and genetic algorithm (GA), the specific critical buckling load (p ¯ c r) which is defined as the ratio of critical buckling load (P cr) to plate weight (gr) has been minimized and the optimal dimensions for cut-out parameters including the ratio of the large diameter of the ellipse (z = 20 m m) to the small diameter of the ellipse (b) and oval angles with the horizontal axis (a ∘) are obtained. Using the method of equivalent properties, the trapezoidal core is transformed into an equivalent orthotropic core and finally the desired structure is transformed into a three-layer sandwich plate including homogeneous upper and lower layers and an orthotropic middle layer. By using the meshless method based on radial and polynomial functions and with the help of the finite element method, the numerical simulation of buckling and free vibration of the sandwich plate has been done. The results showed that the estimation of the buckling load with the vibration correlation technique (VCT) corresponds to the actual condition of the structure, so that due to the high quality of sandwich plate construction and its integrity, the results obtained from the first, second, and third methods of the VCT show the effectiveness of this method for predicting of the buckling load of the structure. [ABSTRACT FROM AUTHOR]

• Introduced a novel formula for helical spring buckling under combined loads. • Experimental and numerical analyses confirm the formula's effectiveness. • Higher preload and prestretching enhance spring buckling torque resistance. A new formula is introduced to analytically determine the critical torsional load or angle of rotation that confers instability in a tension spring under combined tension and torsion load using the theoretical framework of Greenhill's problem applied to an elastic bar as a starting point. The formula's effectiveness is evaluated with experimental torsion tests and finite element method simulations in Abaqus. The results demonstrate the formula's accuracy in predicting instability within specific stretched operating ranges, and achieving a relative error in correlation below 10 % for most operating points. The study underscores the significance of preload and pre-stretching in enhancing the spring's resistance to buckling. [ABSTRACT FROM AUTHOR]

Semi-crystalline polymers is an important group of materials that is used in a vast array of products. In this study, the rate-dependent properties of high-density polyethylene (HDPE) are investigated, both experimentally and theoretically. Experimental compression testing of a three-dimensional HDPE structure is performed and analysed numerically by use of the finite element method. In addition, an Eulerian constitutive material model for isotropic, semi-crystalline polymers is proposed. The model is able to account for such essential phenomena as strain-rate dependence, work hardening, pressure-dependence of inelastic deformations, and damage. The proposed material model was implemented in Abaqus as a VUMAT, which is an explicit implementation. The material model was calibrated by use of uniaxial tensile tests performed on HDPE dog-bone shaped samples, and the model was further explored by applying the VUMAT implementation to the compression tests of the HDPE structure. The simulation model was able to reproduce the experimental results well, both the uniaxial tests and the compression tests. In particular, the friction present in the compression tests seems to play an important role in determining the buckling mode of the structure. • Experiments on high-density polyethylene: compression testing of a 3D structure. • Modelling of rate-dependent inelasticity and damage of semi-crystalline polymers at finite strains using an Eulerian formulation. • Analyses of rate-dependent buckling of the 3D structure. [ABSTRACT FROM AUTHOR]

The buckling behaviors of 2D structures with periodic elliptical holes were studied through numerical simulations and theoretical analysis. A theoretical model was established for the modal analysis corresponding to different buckling modes. The analysis results indicate that, there is a transformation between the buckling modes of the 2D structure with elliptical holes, with the change of the geometrical parameters of the holes. The theoretical analysis and the numerical results match up. Furthermore, in the numerical simulation, a modified force boundary condition for a unit cell under negative pressure activation, being different from the displacement loading, should be considered to ensure the completeness conditions are fulfilled. The confusion in the application of appropriate boundary conditions for the unit cell will result in errors. The choice of the unit cell and the derivation of correct boundary conditions, combined with finite structures, were discussed. [ABSTRACT FROM AUTHOR]

Buckling design of axially compressed cylindrical shells is still a challenging subject considering the high imperfection-sensitive characteristic in this kind of structure. With the development of various design methods, the energy barrier concept dealing with buckling of imperfection-sensitive cylindrical shells exhibits a promising prospect in recent years. In this study, buckling design of imperfection-sensitive cylindrical shells under axial compression based on the energy barrier approach is systematically investigated. The methodology about buckling design based on the energy barrier approach is described in detail first taking advantage of the cylindrical shells whose buckling loads have been extensively tested. Then, validation and discussion about this buckling design method have been carried out by the numerical and experimental analyses on the cylindrical shells with different geometrical and boundary imperfections. Results in this study together with the available experimental data have verified the reliability and advantage of the buckling design method based on energy barrier approach. A design criterion based on the energy barrier approach is therefore established and compared with the other criteria. Results indicate that buckling design based on energy barrier approach can be used as an efficient way in the lightweight design of thin-shell structures. [ABSTRACT FROM AUTHOR]

Motivated by applications of soft-contact problems such as guidewires used in medical and engineering applications, we consider a compressed rod deforming between two parallel elastic walls. Free elastica buckling modes other than the first are known to be unstable. We find the soft constraining walls to have the effect of sequentially stabilizing higher modes in multiple contacts by a series of bifurcations, in each of which the degree of instability (the index) is decreased by one. Further symmetry-breaking bifurcations in the stabilization process generate solutions with different contact patterns that allow for a classification in terms of binary symbol sequences. In the hard-contact limit, all these bifurcations collapse into highly degenerate 'contact bifurcations'. For any given wall separation at most a finite number of modes can be stabilized and eventually, under large enough compression, the rod jumps into the inverted straight state. We chart the sequence of events, under increasing compression, leading from the initial straight state in compression to the final straight state in tension, in effect the process of pushing a rod through a cavity. Our results also give new insight into universal features of symmetry-breaking in higher mode elastic deformations. We present this study also as a showcase for a practical approach to stability analysis based on numerical bifurcation theory and without the intimidating mathematical technicalities often accompanying stability analysis in the literature. The method delivers the stability index and can be straightforwardly applied to other elastic stability problems. [ABSTRACT FROM AUTHOR]

• - Transverse stiffeners behavior under compression; • - Experimental results of unstiffened and stiffened panels under compression (intermediate and edge stiffeners); • - Numerical analysis of transversally stiffened panels and their representative cross sections; • - Analytical analysis of the determination of the critical strength of stiffened panels. The web panels of metal sections subjected to compression have resistances that are often driven by local buckling. Transverse stiffeners are used to increase their resistance. These stiffeners can be arranged at different positions in relation to the edge of the metal section. The strength of the stiffened panel can be compared to that of a compressed element whose cross-section consists of the stiffener and a participating length of the web. To observe the behavior of these stiffened walls and to evaluate the existing analytical calculation methods, an experimental campaign was carried out on two metal sections of different heights, stiffened or not over their entire height of the web. Thus, 33 zones of stiffened or unstiffened panels are tested in double localized compression until failure. The stiffeners are placed near the edge or in the middle of the panel and welded on both sides of the web over its entire height and on the panel flanges. In parallel, a finite element model using shell elements and non-linear calculations considering the plasticity of the materials, the geometrical imperfections and the large displacements is set up. It is validated by comparing its force–displacement curves and modes of ruin with those obtained by tests. The model thus validated makes it possible to enrich the results of the experimental tests to better describe the behavior of stiffened walls subjected to compression. It also allows to discuss the observed failure modes and some analytical formulas which estimate the resistance capacities of the stiffened panels. [ABSTRACT FROM AUTHOR]

This paper deals with optimizing smeared extensional stiffness ratio of stiffeners to that of skin of laminated composite hat-stiffened panel with the variation of pitch length stiffeners, depth of stiffeners and panel orthotropy ratio for three different plie configurations to maximize buckling capacity of the panel. Critical buckling load and global buckling mode shape of the laminated composite hat-stiffened panel are studied for the design of lightweight structures. Parametric studies of hat-stiffened panel under in-plane compressive load are presented with simply supported boundary conditions. Models are analyzed by applying Finite Element method using ABAQUS. A database is provided based on smeared stiffness approach for two different hatstiffened (600-hat-stiffened and 750-hat-stiffened) panels with variation of pitch length stiffeners, depth of stiffeners, panel orthotropy ratio and smeared extensional stiffness ratio of stiffeners to that of skin with three different plie configurations. On the basis of the study, optimum smeared extensional stiffness ratio is increased with increasing of orthotropy ratio for all similar skin, but it is also increased with decreasing extensional stiffness ratio to maximize buckling capacity of hat-stiffened panel and general guidelines are developed for the design of better hat-stiffened panel. [ABSTRACT FROM AUTHOR]

In this study, a 2D axisymmetric numerical model is developed for simulating buckling of suspension droplets for processes with a high evaporation rate. This model not only demonstrates droplet distortion during buckling but also predicts and visualizes solid particles' behavior inside the droplet. The core element of the simulation method is the so-called D3-law predicting the droplet size and shape during different stages of the process. For improving the accuracy in the droplet shape and forces exerted on the solid particles, the effect of solid particles' concentration on buckling process has been considered. In this method, the solid particles are modeled in Lagrangian manner and possible collision of particles during the buckling has been considered. It is shown that the role of capillary forces in the shape of agglomerated particles is significant. The numerical results also reveal that the size of agglomerated particle depends on the initial solid particle fraction and the suspension droplet size. For all cases considered, the results are in good agreement with experiment measurements reported in the literature. [ABSTRACT FROM AUTHOR]

Loss of furniture stability may constitute a rapidly occurring, direct hazard to the user's life or health. Studies conducted to date have concerned the effect of the type of material and method of back wall attachment on its stability. In contrast, practically no analogous data are available on the stability of side walls. In the case of loading with a vertical force applied on a furniture item supported at three corners all the elements are subjected to torsional strain. However, the static pattern changes when the structure is supported at four corners. Then loading of a piece of furniture with a vertical force results in slight displacements in the direction of the acting force, whereas buckling and considerable deflections are perpendicular to the direction of that load. This has a significant effect on side wall stability. For this reason it was decided in this study to determine the effect of side wall structure on stability (buckling) and postbuckling behaviour of side walls in cabinet furniture. The analyses consisted in numerical calculations using the Finite Element method. Three types of side wall structures were used: particleboard, honeycomb panel and board-on-frame. Values of critical forces, lateral deflections and normal stresses in the direction of the acting load were calculated. Testing results confirmed that the honeycomb panel provides the most advantageous structure for side walls. [ABSTRACT FROM AUTHOR]

A built-up I-section with web stiffeners and complex edge stiffeners is expected to have better performance to resist against local and distortional buckling compared to conventional built-up I-section. In order to study the influence of perforations on compression behavior of above section forms, a series of pin-ended compression tests and numerical analysis on perforated double-limb cold-formed steel built-up I-section columns with complex edge stiffeners and web stiffeners were conducted. The test specimens contained 12 concentrically loaded specimens and 8 eccentrically loaded specimens with two cross-section shapes, respectively. The test results were found that the web stiffeners could obviously increase the ultimate bearing capacity of the built-up members, especially for stub and medium-long columns. The ultimate bearing capacity of two cross-section shaped medium-long columns decreased gradually with the increase of eccentricity. Two adjacent single-limb webs of conventional built-up I-section could provide support to each other. The web stiffeners restricted the deformation of the plate around the holes effectively, but it also weakened the composite action between the single-limb webs. A finite element model was developed and verified against experiments of perforated built-up columns. Furthermore, a total of 96 parametric analyses were completed to investigate the optimal ratio of the hole depth to web sub-element in the Σ-shaped built-up I-section perforated columns. Finally, two types of direct strength method formulas were used to calculate the ultimate bearing capacity of perforated built-up specimens. The appropriateness of those direct strength method was compared. It was shown that the existing direct strength method formulas were both valid for perforated built-up I-section columns with complex edge stiffeners. [ABSTRACT FROM AUTHOR]

Mechanical properties are investigated for a class of microstructured materials with promising applications. Specifically, we consider a composite material with orthogonal, mutually interconnected fibers building a pantographic substructure. In order to predict the behavior of such a system in three-dimensional continuum, a reduced-order model is introduced by means of a bi-dimensional elastic surface accurately describing large deformations. The properties of this reduced-order model are characterized by an elastic energy density that involves second space derivatives of the displacement for capturing the resistance of twisted and bent fibers in plane as well as out of plane. For determining the coefficients in the elastic energy of the reduced-order model, we utilize a numerical inverse analysis and make use of ad hoc computational experiments performed by a direct numerical simulation on the microscale with detailed modeling of the pantographic substructure. This reduced-order model represents a homogenized material on macro-scale with its substructure on microscale. The homogenized model is capable of describing materials response at a significantly less computational cost than the direct numerical simulations. [ABSTRACT FROM AUTHOR]

• Yielding in steel beams varies with moment distribution and residual stresses. • Yielding reduces effective in-plane and out-of-plane section rigidities. • In-plane moment distribution in continuous beams is affected by reduced rigidities. • Lateral buckling resistance is affected by moment distribution and reduced rigidities. • Buckling prediction requires iterative numerical analysis. The inelastic behaviour of a steel beam is complicated by reductions in the section rigidities which depend on the moment distribution and residual stress pattern. The inelastic beam is effectively tapered and mono-symmetric, and iterative numerical methods need generally to be used for the analysis. The in-plane moment distribution in an inelastic continuous beam lies between the commonly assumed rigid-plastic "plastic" path and a "yield" moment path. The yield path is the more critical for lateral buckling of the continuous beams considered in this paper. Approximations of the inelastic out-of-plane moduli of continuous beams developed from closed form lateral buckling solutions for simply supported beams in uniform bending can be used in a computer program for the buckling analysis of tapered mono-symmetric beams. Residual stresses cause significant reductions in the inelastic buckling resistance. The AISC design code predicts strengths which are similar in shape but significantly higher in magnitude than the inelastic buckling resistances of simply supported beams in uniform bending. The predictions for beams with central concentrated loads are much higher than the corresponding inelastic buckling resistances. Closer but still conservative approximations are obtained by using the method of design by inelastic buckling, which can also be used for continuous beams. This method is much simpler than those used to obtain accurate predictions. [ABSTRACT FROM AUTHOR]

This work investigates the interplay between viscoelasticity and instabilities in soft particulate composites undergoing finite deformation. The composite is subjected to in-plane deformation at various constant strain rates, and experiences microstructural buckling upon exceeding the critical strain level. We characterize the dependence of the critical strain and wavelength on the applied strain rate through our numerical analysis. In the simulations, we employ the single and multiple-branch visco-hyperelastic models. We find that the critical strain and wavelength – characterized by the single-branch model – show a non-monotonic dependence on the strain rate, reaching a maximum at a specific strain rate. Remarkably, different buckling patterns (with different critical wavelengths) can be activated by changing strain rates. The space of admissible buckling modes widens in composites with higher instantaneous shear modulus. In the composites characterized by the multiple-branch model, the critical strain function exhibit multiple local maxima following a superposition of the single-branch responses. Typically, the branch with a larger relaxation time has a more significant effect on the critical strain. Moreover, the local maximum (of the critical strain function) is amplified by increasing the strain–energy factor of the corresponding branch term. Finally, we perform the experiments on the 3D-printed particulate soft composite characterized by a broad spectrum of relaxation times. The comparison of the experimental and simulation results demonstrates the ability of the numerical model to predict the critical buckling characteristics. [ABSTRACT FROM AUTHOR]

In this paper, we present a numerical analysis of the buckling of elastic thin structures by using Asymptotic Numerical Method (ANM) and Padé approximants. We consider the case of cylindrical shells submitted to external pressure and we show how the perturbation technique can be applied for conservative and non-conservative loadings. A shell formulation well adapted to thin structures and which uses the Enhanced Assumed Strain (EAS) concept and a three-dimensional constitutive law without condensation is considered in this study. Numerical examples are presented with comparison between conservative and non-conservative loading in term of critical pressure. • Numerical analysis of the buckling of elastic thin structure submitted to external pressure. • Asymptotic Numerical Method, and Padé approximants are successfully used. • The external pressure is considered as a non-conservative, follower loading on the thin structure. • Büchter-Ramm finite elements and EAS assumption have been used. [ABSTRACT FROM AUTHOR]

Abstract The buckling load parameters of the graded nanotube sandwich structure reported in this article under the influence of uniform thermal loading. The corresponding properties of the graded nanotube sandwich evaluated via the extended rule of mixture including temperature dependent properties of each constituent. The nanotube structural model derived mathematically using a higher-order polynomial displacement to maintain the required shear stress continuity and thermal distortion via Green-Lagrange strain. Further, the variational technique is adopted to obtain the governing equilibrium equation of the sandwich structural panel and the subsequent algebraic form achieved using the isoparametric displacement finite element steps. The computational buckling load parameter predicted using the own MATLAB code with the help of the current mathematical model. The model accuracy and the consistency are established through simultaneous convergence and validity study with available published results. Finally, the detail applicability of the current higher-order model is highlighted through a series of numerical examples and corresponding inferences. [ABSTRACT FROM AUTHOR]

The study investigates the effect of eccentric load on the stability and post-critical states of thin-walled composite top-hat cross-section columns made of CFRP under compression. The specimens were subjected to compressive load on the universal testing machine Zwick Z100 with regard to both axial and eccentric compressive loads. On the basis of the experimental studies, numerical models of thin-walled composite profiles were designed and verified by numerical analysis based on the FEM. The first stage of the conducted studies was performing a linear buckling analysis of stability of composite structures. The second stage of the analysis involved performing a nonlinear analysis of the thin-walled structures with geometric imperfections reflecting the lowest buckling modes. The obtained test results showed various effects of non-axial compressive load on the critical load values and stiffness of the construction in the post-critical state. In the case of eccentric loading in the direction parallel to the web of the top-hat profiles, the critical load values practically did not change – a drop in the force did not exceed 1.5%, as well as there was no change in the stiffness of the structure in the post-critical state. The realization of the eccentricity in the direction perpendicular to the profile web caused a drop in the critical force equal 43% and a significant decrease in the stiffness of the structure. On the other hand, implementation of the eccentricity load toward the web caused an increase in the critical force by more than 20%, despite very small eccentricity values of only 4 mm were applied. This proved high sensitivity of the tested structures to the non-axial load in the direction perpendicular to the web of the profile. The FEM results and the experimental findings showed satisfactory agreement. [ABSTRACT FROM AUTHOR]

Abstract This paper was dealt with buckling and post-buckling behavior of short thin-walled Z-columns made of a carbon-epoxy laminate, subjected to eccentric compressive load. The buckling mode and the buckling load of real structures versus load eccentricity were discussed. The study involved both experimental tests were carried out on real laminated structures and numerical simulations by the finite element method. The buckling load of real structures was determined by approximation methods on the basis of experimental and numerical post-buckling equilibrium paths of the structure. Additionally, in numerical simulations, the bifurcation load value was determined by solving an eigen problem. In all cases, experimental findings and numerical results show high agreement. The study determined the quantitative influence of the direction and value of compressive load eccentricity on the buckling load and rigidity of the structure in the post-buckling state. [ABSTRACT FROM AUTHOR]

Highlights • The mathematical model of corrugated shells with special shapes is presented. • Effect of corrugation parameters on critical load is investigated. • Linear and nonlinear buckling analyses are conducted. • Critical load of corrugated shells is compared to smooth ones. • Specific range of corrugation parameters significantly increase the value of relative critical load. Abstract The problem of elastic stability of the shells with special shapes with corrugated middle surfaces under external pressure is debated in the presented paper. Solution of the problem is based on FEM study. Corrugated barrelled, pseudo-barrelled, and cylindrical shells of constant mass are considered. Geometrical modification of the middle surface geometry is based on sine wave along principal directions. Middle surface of the corrugated shells are described referring to differential geometry of surfaces by parametric functions in three-dimensional Euclidean space. Linear and nonlinear buckling analyses are conducted. Examples of buckling modes are presented, which differ significantly from those typical for shells of revolution with positive or zero Gaussian curvature. It is proven that corrugation may lead to serious increase or decrease of critical load for all types of presented shells. [ABSTRACT FROM AUTHOR]

Highlights • Nonlinear finite element model of built-up section were developed and verified. • A proposed design approach is presented using direct strength method (DSM) • The proposed approach is evaluated by comparing with the current existing method and FEA data. • A parametric study showing the influence of D1/B ratio on the stability and strength of the built-up columns. Abstract This paper, based on new proposed approaches, is a numerical investigation of the behavior of thin-walled cold-formed steel built-up columns under a uniform compression. Two types of cross sections have been studied, built-up closed and open sections formed by two channels connected by battens plates. First, a nonlinear finite element model has been developed and the results obtained show a good agreement against experimental results, such as the ultimate strength, the type of deformed shapes at failure and the lateral displacement. Second, a new proposed approach based on the DSM approach where the local, distortional or global buckling has been obtained numerically, using finite element method software, the thickness at the contact area in the web is taken as 1.0 times the thickness of the plate "t", instead of 1.5 or 2.0 times "t". In this case, the compound section is acting as one rigidly connected section. Comparisons with experimental data give a satisfactory degree of accuracy in the proposed design method (DSM-t) and the results are more conservative than those found by the DSM-1.5 and DSM-2. The results, for either closed or open sections, are also slightly conservative for columns failing in global modes than in local ones, if compared with the AISI and EC3 specifications. Some parameters, such as the spacing channels-web length ratio (B1/D) influence the stability and strength of the built-up columns. [ABSTRACT FROM AUTHOR]

Abstract In this study the dynamic stability of viscoelastic functionally graded cylindrical shells (VEFGCSs) under an axial load with different initial conditions is investigated. Mathematical models are constructed for the problem of dynamic stability of the VEFGCSs, which is characterized simultaneously by taking into account both viscoelastic and FGM features. The basic equations of VEFGCSs are described by integro-differential equations using the linear viscoelasticity theory. An approach is developed to the determination of the critical times (CTs) for VEFGCSs with different initial conditions. Finally, the numerical analyzes are performed to demonstrate the influences of the initial conditions, the FGM profiles and the rheological parameter on the critical times for various geometric characteristics of the cylindrical shells. Highlights • Dynamic stability of Viscoelastic FG cylindrical shells (VEFGCSs) is investigated. • The basic equations of VEFGCSs are described by integro-differential equations. • Formulas for critical time of VEFGCSs with different initial conditions are obtained. • Analysis is performed for various types of VEFGCSs and rheological parameter. [ABSTRACT FROM AUTHOR]

The aim of this research is to examine the mechanical buckling behavior of multi-layered functionally graded beams in the axial direction. Numerical buckling analyses were performed using finite element software called ANSYS. Each beam configuration is suggested to be three layers prepared using various percent volume fractions of Zirconia (ZrO2) and Aluminum (Al) materials. The levels of layers and layer positions of the beams were evaluated according to Taguchi's L9 (33) orthogonal array technique. Layers were determined as control factor and so nine numerical analyses were performed under clampedclamped boundary conditions. The first mode shapes of the axially layered functionally graded beams were demonstrated in order to detect the most affected layers as visually. Analysis of signal-to-noise ratio was applied to obtain the optimum levels of layers. Analysis of Variance (ANOVA) was employed to solve the layers with significant impacts and their percent contributions on numerical results. The maximum buckling load was determined using various positions of layers with the optimum levels obtained based on Taguchi methodology. [ABSTRACT FROM AUTHOR]

Abstract This research work presents a parametric numerical study on the resistance at elevated temperatures of stainless steel members, subjected to combined bending and axial compression. Previous studies have shown the need for the development of further research works aiming at better predicting the fire behaviour of stainless steel beam-columns. However they have only considered beam-columns composed of stocky I sections. Hence, this paper focuses on austenitic stainless steel (European grade 1.4301 also known as 304) beam-columns composed of square hollow sections (SHS) and circular hollow sections (CHS), considering different cross-sections classes (1 to 4), according to Eurocode 3 (EC3) classification. The numerical analyses were performed using the finite element program SAFIR, with material and geometric non-linear analysis considering imperfections. The influence of the following parameters was evaluated: bending moment diagram shape, cross-section slenderness considering the local buckling occurrence on the thin-walled sections, and member slenderness for the global instability due to flexural buckling. Comparisons between the obtained numerical results and the interaction curves of Eurocode 3 are presented. The results show that specific design approach should be developed for these stainless steel members under fire situation, taking into account the above mentioned parameters. Highlights • The behaviour of stainless steel beam-columns with square and circular hollow sections in case of fire is studied • Numerical analysis with material and geometric imperfections of stainless steel structural elements are performed • The accuracy and safety of EC3 design for beam-columns are not suitable for these stainless steel members in fire. [ABSTRACT FROM AUTHOR]

Abstract Global buckling failure should be avoided when designing a structure with the requirement of crashworthiness performance. This study characterises the quasi-static in-plane crushing of CF/EP composite sandwich panels by tailoring their bevel angles. A finite element model was developed describing the interlaminar and intralaminar damage of a composite sandwich panel; this model was validated by in-plane compression experiments. A numerical analysis and compression experiments were then performed to determine the responses and failure modes in the CF/EP composite sandwich panels with various bevel angles. The results showed that the global buckling-to-progressive failure transition under compression occurred in the composite sandwich panels when the bevel angle reached a critical value. A microscopic analysis showed that the composite sandwich panels with buckling failure behaviours exhibited an apparently classical post-buckling transverse shearing mode, while those with progressive failure presented individual lamina bending with inward and outward fronds. This study provides some useful data for the design of the crashworthiness of a sandwich composite panel by introducing a progressive failure mode. [ABSTRACT FROM AUTHOR]

This paper focuses on two opening reinforcement methods of spherical shells under uniform external pressure. To reduce the local weakening and buckling effects of openings in spherical shells, designs comprising the wall reinforcement and the combination of a wall and thick plate reinforcement were employed to minimize buckling instability. In addition, the equal-proportion models of two kinds of reinforcement methods were manufactured and tested. The geometry, thickness, buckling load, and final collapsed mode were measured for each spherical shell with opening reinforcement. The paper contains a comparison between theoretical predictions, numerical analysis results and experimental data for two reinforced spherical shells. The theoretical and numerical results were in good agreement. The numerical solution result, obtained by considering the real defect, was consistent with the experimental result, and the failure mode was consistent with the location of the defect. [ABSTRACT FROM AUTHOR]

Understanding the buckling and post-buckling behavior of rods confined in a finite space is of both scientific and engineering significance. Under uniaxial compression, an initially straight and slender rod confined in a tube may buckle into a sinusoidal shape and subsequently evolve into a complicated, three-dimensional (3D) helical shape. In this paper, we combine theoretical and numerical methods to investigate the post-buckling behavior of confined rods. Two theoretical models, which are based on the inextensible and extensible rod theories, respectively, are proposed to derive the analytical expressions for the axial compressive stiffness in the sinusoidal post-buckling stage. The former is concise in formulation and can be easily applied in engineering, while the latter works well in a broader scope of post-buckling analysis. Both methods can give a good approximation to the sinusoidal post-buckling stiffness and the former model is proved to be a zeroth-order approximation of the latter. The flexible multibody dynamics method based on the Timoshenko's geometrically exact beam theory is used to examine the accuracy of the two models. The methods presented in this work can be used in, for example, drilling engineering in oil and gas industries. [ABSTRACT FROM AUTHOR]

This work is a contribution to the understanding of the nonlinear shear behaviour caused by cell postbuckling in Nomex honeycomb cores. First, an experimental benchmark study was made of different designs for the shear testing of honeycomb cores. Then, several test specimens were fabricated and tested, a 3D DIC system being used to measure and record the displacements. An Artificial Neural Network (ANN) was also used to identify the onset of bucking and collapse of the cells. The influence of the overall boundary conditions of shear tests on the buckling of the cells is presented both experimentally and numerically. The reversibility and test procedure results suggest that it may be possible to allow the shear strength to be increased by up to 35% under certain conditions. [ABSTRACT FROM AUTHOR]

Fabrication of ship structures involving welding of thin plates, poses a real challenge in limiting the out-of-plane distortion due to buckling. In this study, the effect of thermo-mechanical tensioning (TMT) on minimizing out-of-plane distortion due to buckling in fabrication of stiffened panels has been investigated through experimental and numerical studies. Experiments were conducted using 3-mm-thick plates. The pretensioning of the plates was done along the stiffener welding lines using the shrinkage forces of the tensioning lugs. The lug width was decided based on the possible width of the tensile stress zone due to the welding of stiffener. The tensioning lugs were heated to a temperature so that the plastic deformation of the lugs are minimized thereby required tensioning of the plate could be achieved. Through the implementation of TMT, a noticeable reduction in the out-of-plane distortions were observed. The influence of the sequence of lug removal on the buckling distortions was studied numerically. Fairly good agreement was obtained between experimental and numerical results. The process of TMT was found to be quite effective as an active in-process distortion mitigation technique for fabrication of thin stiffened panels. [ABSTRACT FROM AUTHOR]

The buckling and free vibration of initially stressed functionally graded cylindrical shell reinforced with non-uniformly distributed graphene platelets (GPLs) are investigated using the state-space formulation based on three-dimensional elasticity theory. The shell is under an axial initial stress and composed of multilayers with GPLs uniformly dispersed in each individual layer but its weight fraction changing layer-by-layer along the thickness direction. The modified Halpin-Tsai model and rule of mixtures are employed to evaluate the effective elastic properties of the GPL-reinforced shell. Analytical buckling and frequency solutions are obtained for simply supported shells. Numerical results are presented for functionally graded GPL-reinforced cylindrical shells with five GPL dispersion patterns (GPL-UD, GPL-V, GPL-A, GPL-X, and GPL-O). The effects of GPL weight fraction, dispersion pattern, geometry, and size as well as the influence of initial stress on the buckling and free vibration characteristics of the shell are discussed in detail. It is found that the addition of a small amount of GPLs significantly increases the critical buckling stress and natural frequencies. The GPL-X pattern outperforms other patterns for thin composite shells while the uniform pattern GPL-UD works better for thick composite shells. [ABSTRACT FROM AUTHOR]

The problem addressed in this paper is the thermal buckling behaviour of thin-walled steel cylindrical fixed-roof tanks under non-uniform loading, induced by an adjacent tank. This specific type of thermal loading can be triggered by a neighboring tank fire where heat is transferred mainly through radiation. Since the calculation of the temperature field of the heated tank lies in other scientific fields (e.g. Computational Fluid Dynamics), a thermal pattern, proposed in literature, is used for the simulation of the fire-induced load and the investigation of the structural response of the tank due to heating. The study is conducted numerically through the Finite Element method, using coupled thermo-mechanical analysis. The general purpose Finite Element code MSC Marc, is used for the simulation. Three-dimensional models are developed using shell elements. Firstly, a detailed study of the failure mechanisms that take place in case of non-uniform loading is carried out. Furthermore, tanks with different geometries are studied. The main objective is the calculation of the critical temperature i.e. the temperature where the failure appears and the determination of the failure modes. Finally, a parametric study is conducted for the evaluation of the effectiveness of stiffening methods that are commonly used at ambient temperature design (stiffeners and stepwise wall thickness), in the case of the non-uniform heating load. In this study, the heated tanks are considered to be empty, which is the most severe scenario, for their structural integrity. [ABSTRACT FROM AUTHOR]

A numerical investigation on the buckling resistance of FGM plates having parabolic-concave thickness variation exposed to in-plane loading is presented in this piece of research work. An analytical formulation is derived and the governing differential equation of stability is solved numerically using finite difference method. A specific function of thickness variation is introduced, where this function controls the parabolic variation intensity of the plate thickness without changing its original material volume. The results indicated that the loss ratio in the buckling resistance due to parabolic-concave thickness variation is highly dependent on the geometrical properties of the plate, while it is not affected by the material properties or by the distribution profile of the constituent materials. Influencing material and geometrical parameters on the degradation of the buckling resistance are investigated, which may help in design guidelines of such complex structures. [ABSTRACT FROM AUTHOR]

In this paper, we investigate global and local stability of columns with an open and a closed thin-walled cross section. The proposed model of global stability is made of two deformable elements connected with an elastic joint. Stiffness of the elastic joint represents local discontinuity of the cross section of the column caused by the loss of stability of individual plates. The model of local stability of the columns is conceptualized on the principle of continuity of individual plates of the cross section. The coefficients of local buckling are defined as geometric parameters of the column with a rectangular hollow section (RHS) and a U-shaped cross section. The dominant parameters that influence the interactive behaviour of local and global buckling are the slenderness of plates and the column as a whole. The basic function of the developed models is to identify the stability mechanism in terms of better estimation of the critical force and higher load capacity. [ABSTRACT FROM AUTHOR]

GPa-grade steels which possess the ultimate tensile strength over 1000 MPa and higher elongation have been thoroughly researched to replace conventional high-strength steels in automobile industry to enhance fuel efficiency without sacrificing crashworthiness. However, high strength of GPa-grade steel does not only induce punching pin buckling due to high contact pressure, but also abrasive wear on the mold surface due to the unstable contact that results from the large amount of springback, which tend to impede widespread usage of GPa-grade steels. In this research, design criteria for an optimal aspect ratio of the punching pin preventing buckling failure has been proposed by linking with experimental and numerical analyses, which is validated with the analytic solutions. Furthermore, in order to prevent stripping failure, it is highly recommended that one of the main factors, a blank holder force (BHF), over 1.5 MPa has to be maintained during the withdrawal process to minimize the effect of springback in stamped panels applying GPa-grade steel, which is able to extend the tool life of the side punching pin about 100,000 cycles. [ABSTRACT FROM AUTHOR]

The work of this paper deals with the in-plane material optimization with the objective of minimizing the amount of the nano-reinforcement required to satisfy the desired buckling constraints. The minimization of the reinforcement is necessary for nano-reinforced composites because the price of the reinforcement is very high. Three types of panels are considered; (1) unstiffened panel, (2) panels with cutouts, and (3) stiffened panels. The in-plane distribution of the reinforcement is represented using the polynomial expansion technique which is also extended to model non-rectangular domains via coordinates transformation. It was found that material grading can saves a very significant amount of the reinforcement up to 200% relative to homogenous panels. The saving of the reinforcement depends on four factors; (1) the problem nature, (2) the boundary conditions, (3) the applied loads, (4) the direction of the material gradings. [ABSTRACT FROM AUTHOR]

In this work, the overall behavior of finite dimensional metallic foam specimens under axial compression is derived from a mixed analytical and numerical framework based on the buckling pattern that the walls of the foam exhibit in this situation. Instead of a full simulation of the entire foam, the present approach requires the simulation of three compression cases of representative volume elements and works on a finite dimensional context instead of the infinite periodic boundary consideration. Results obtained with the present framework are compared with those obtained using full finite element simulation, exhibiting excellent agreement even at very large strains. [ABSTRACT FROM PUBLISHER]

A composite material system comprised of a monostable negative stiffness (NS) structure within a polymer matrix was designed, fabricated, and experimentally evaluated. The monostable negative stiffness (NS) structure was designed using a combination of analytical and numerical models and manufactured in stainless steel. The NS structure was arranged in parallel with different polymer matrices to experimentally evaluate the effects of the matrix properties on the overall stiffness and energy dissipation of the composite NS-matrix system when loaded in uniaxial compression. A strong influence of the matrix properties on the stiffness and energy absorption capacity of the composite system was observed. Unlike conventional composites for which there is a natural tradeoff between stiffness and energy absorption capacity, the composite NS-matrix system enhanced stiffness while simultaneously improving energy absorption relative to a neat matrix, but only when the stiffness of the matrix was carefully matched to the stiffness of the NS structure. [ABSTRACT FROM AUTHOR]

The various assessment methods of ultimate strength for hull girder of ships or offshore structures might lead to different results and computation time. The nonlinear finite element (FE) analyses include the implicit static analysis and explicit dynamic analysis, which both can consider the large deflection and material nonlinearity during the process of progressive collapse. Comparing with the implicit static analysis, the explicit dynamic analysis can consider the transient influence of time and avoid the convergence issue in iterative procedure. The object of the present paper is to figure out a reliable and suitable FE modelling in the explicit dynamic method, which could keep the balance of the acceptable accurate results and computation resources. Several influential factors on the collapse behaviours of hull girder are discussed including boundary conditions, geometric ranges of finite element model, element types, loading methods and loading time. The results of a Suezmax oil tanker and Reckling models assessed by the explicit dynamic method are compared with that by the other analytical methods or in the experiment. [ABSTRACT FROM AUTHOR]