Search

• The low-restraint GLARE is taken as a research object and its deformation characteristics and failure mode are studied using uniaxial tensile, bending experiments and numerical simulation in this paper. • Based on experimental observations, it is found that the low-restraint GLARE produces the phenomenon of interlayer slip, and the interlaminar residual stress is much smaller than the cured laminate, whereas the deformation limit and performance are improved. • The results of bending experiments revealed that the load variation of low-restraint laminate is significantly different from the cured laminate during bending. • The low-restraint GLARE does not obviously delaminate and fracture during bending due to the low interlayer residual stress and a certain degree of interlayer slipping, exhibiting a significant improvement in the bending forming limit. • This paper provides theoretical bases for the in-depth analysis of deformation properties and forming laws of low-restraint GLARE, guiding further applications of laminates. Fiber metal laminates (FMLs) possess a better weight reduction effect than traditional metal materials due to the coupling properties of heterogeneous materials, showing promise in the areas of aviation and aerospace. At present, the research on FMLs mainly focuses on the deformation properties after curing while the mechanical properties in the low-restraint state, i.e. the laminates are temporarily not cured and are formed under lower constraint stresses, are not studied in detail. Herein, the low-restraint GLARE is taken as a research object and its deformation characteristics and failure mode are studied using uniaxial tensile, bending experiments and numerical simulation in this paper. Moreover, the influence of key parameters, such as temperature, laminate structure and span length, is investigated, as well as the tensile and bending deformation behavior of GLARE in a low-restraint state is obtained. In addition, based on experimental observations, it is found that the low-restraint GLARE produces the phenomenon of interlayer slip, and the interlaminar residual stress is much smaller than the cured laminate, whereas the deformation limit and performance are improved. This paper provides theoretical bases for the in-depth analysis of deformation properties and forming laws of low-restraint GLARE, guiding further applications of laminates. [ABSTRACT FROM AUTHOR]

• A novel non-linear numerical model for thin-walled members is presented. • Four classes of H-section members are selected to study the hysteretic behaviour. • The comparison of test results and those of the proposed model is accomplished. • The deformation mode, buckling effects, and material nonlinearity are considered. Based on Gonçalves's geometrically exact beam theory considering cross-section deformation, the warping and distortional deformation of thin-walled members are described in this paper by means of a combination of section deformation modes. By integrating with the J2 elastic‒plasticity theory for the steel, a numerical model is established for the hysteretic behaviour of thin-walled steel members. Four classes of H-section members are selected on account of the design codes, and the influence of section warping and distortion deformation modes on the calculation of the hysteretic behaviour of components with different section types is analysed. The crucial aspect lies in the bending hysteresis behaviour around the strong and weak axes of the cross-section for H-beam steel members subjected to typical thin-walled members with relatively large widths and thicknesses. Test results on the hysteretic behaviour of H-section steel members are compared with those calculated from the proposed model in terms of the hysteric behaviour of components, strength degradation, energy-dissipating capacity, etc. These findings validate the correctness and feasibility of the established non-linear analysis model for thin-walled members. [ABSTRACT FROM AUTHOR]

• The rapid maximum dynamic stress (S max) prediction method of Miura-ori core sandwich panels with impact defects is proposed, which could directly predict S max with few simulations by establishing the relationship with impact deformation in advance. • S max of sandwich panels will increase by 2.635 times with the impact deformation below 32.1 % of Miura cell projection area. • The impact deformation is predicted by the geometric relationship of Miura creases and material properties, and the prediction errors are below 12.5 %. Miura-ori core sandwich panels have great application potential in aviation aircraft. Subject to the impact and vibration loads, the small impact defect will increase the dynamic stress, resulting in fatigue failure. Moreover, the Miura creases complicate the impact deformation, which is extremely time-consuming to analysis the dynamic stress only through simulation. Therefore, a rapid dynamic stress prediction method for Miura-ori core sandwich panels is first proposed based on the predicted impact deformation by arbitrary defects in this paper. The dynamic stress of sandwich panels could be directly calculated with few numerical results by establishing the relationship with impact deformation in advance. The vibration mechanism of sandwich panels with defects is revealed. Although the deformation area is below 32.1 % of Miura cell projection area, the dynamic stress will increase by 1.984–2.635 times with different defects. The impact deformation is predicted by the geometric relationship of Miura creases and material properties, and the prediction errors of hemispherical and drilling defects with arbitrary defect positions are below 12.5 % and 10.6 %, respectively. Taking two types of defects (hemispherical and drilling defects), different defect depths and positions into consideration, the prediction errors of maximum dynamic stress are from -7.9 % to 16.8 % compared to simulation. [ABSTRACT FROM AUTHOR]

• The bi-modular FGMs UMAT is developed for the first time and successfully conducted to validate the perturbation solution. • The rise-to-thickness ratio and corresponding critical load are two factors influencing the snap-through buckling. • The rotation constraint and radial constraint at the shell edge have opposite effects on the snap-through buckling. • The bi-modular FGM effect may speed up or slow down the snap-through buckling. Functionally graded materials (FGMs) enable structures to achieve a smooth transition between different material properties, providing an optimized combination of functions to meet the diversity of engineering needs. However, the presence of bi-modular effect in FGMs is often neglected due to the complexity in the analysis. In this paper, the curvature correction equivalent method based on the von Kármán theory will be applied to the theoretical study for the large deformation problem and the resulting snap-through buckling of functionally graded revolutionary shallow thin shells with bi-modular effect under different boundary constraints. Furthermore, a bi-modular FGMs user material subroutine (UMAT) is developed for the first time to simulate the real material model, thus validating the theoretical solution. The results show that except for the bi-modular effect of materials, boundary constraints of shells also have important influences on the relationship of load vs. central deflection and snap-through buckling. The research of boundary constraints brings new conclusions to snap-through buckling: the rotation constraint and radial constraint at the shell edge have opposite effects on snap-through buckling. This work will contribute to the analysis of the snap-through buckling of functionally graded revolutionary shallow thin shells with an obvious bi-modular effect and under various boundary constraints. [ABSTRACT FROM AUTHOR]

The present paper focusing on the most important energy absorbing system of the circular thin-walled tubes or shells under lateral compression between two rigid plates, which is also a basic mechanical issue, studies the cross-sectional deformation in terms of the compressive force applying to the tube in the large elastic–plastic deformation stage during the lateral compressive process by both theoretical as well as finite element analysis (FEA) methods. Firstly a FEA simulation for the thin-walled tube's lateral compressive process between two parallel plates is carried out to analyze the mechanical response and deformation characteristics, and then it is validated by tube's lateral compressive experiment using digital image processing technology. Following the simulation results, some assumptions are proposed for theoretical derivation. Secondly focusing on the large elastic–plastic deformation stage (Stage II, in this paper), the compressive deformation of thin-walled tubes is divided into elastic and plastic regions according to the von Mises yield criterion. In elastic region the linear strain–displacement relations of shell theory and Hooke's stress–strain relations are employed, and in plastic region the nonlinear large strain–displacement relations of doubly-curved shell theory and the power hardening rule are employed. Then considering both geometric and material nonlinearities, the equilibrium equation, which is a complicate integral equation with the variable upper limit, is derived using the principle of virtual work. It is solved by expanding the integrand as a set of polynomials power series. Then the predicted cross-sectional deformation in terms of the compressive force can be obtained by the iterative method. Finally some lateral compressive simulations involving various tubes with different geometric parameters are carried out, and the theoretical model is validated by comparison of the cross-sectional profiles predicted by theoretical model with those obtained by the simulations as well as other methods. At the same time, the applicable conditions of this model are discussed. This paper will play a positive role in studying the cross-sectional deformation for various shells under lateral compression in different application areas. • Mechanical response and deformation characteristics are presented by FEA, which have been validated by compressive experiment. • A new theoretical is derived to predict the cross-sectional deformation in the large elastic-plastic deformation stage of the laterally compressed thin-walled tubes. • A new method is proposed to solve the unintegrable equation with the variable upper limit during the theoretical derivation. • The applicable conditions of this model are given. [Display omitted] [ABSTRACT FROM AUTHOR]

Slender tubes constituted of hyperelastic materials undergoing large deformations and conveying inertialess flow of Newtonian fluids are a model representation of several systems including those in soft robotics, biology and in industry. In this paper, we undertake a systematic study of this system. The tube's hyperelastic behavior is modeled by five (5) different constitutive laws: Neo-Hookean, Mooney–Rivlin, Fung, Gent and Ogden. Invoking the principles of finite elasticity, we delineate the local pressure — deformation relationship for the tube for each of the hyperelastic models. The structural mechanical field of the tube is then coupled with fluid flow field, which is simplified using the principles of lubrication approximation. The resultant fluid–structure interaction problem then throws up a set of interesting results including the deformation and pressure profile across the tube, and tube laws for five (5) hyperelastic models. Analyzing these results, we posit that the behavior of Neo-Hookean and Mooney–Rivlin tubes is converse of Fung's and Gent's tubes; the latter show a strain hardening behavior whilst the former exhibit a strain softening one. A sensitivity analysis which underscores the relative importance of geometrical nonlinearity in the problem then follows. • Thin walled hyperelastic tubes conveying inertialess flow analyzed. • Five (5) different models of hyperelasticity analyzed and compared. • Tubes undergo large deformations. • Lubrication approximation for fluid flow used to analyze the FSI problem. • Effect of geometric nonlinearity discussed. [ABSTRACT FROM AUTHOR]

• Giving the deformation mode of stiffened conical shell under deep water burst load. • Giving the trapezoidal deformation function for the deformation of the structure. • Giving the solution model of the maximum displacement of the structure. The reinforced cylindrical and conical column structures are widely used structural forms in underwater vehicle structures. In this paper, the reinforced conical shell structure in the transition compartment of underwater vehicles was used as the research object. Based on the shock wave propagation theory and ABAQUS acoustic structure coupling numerical simulation method, the numerical simulation model of conical shell structure under deep-water explosion load was established. The deep-water explosion simulation of conical shell structure under the conditions of different water depths, charges and explosion distances was carried out, and the deformation and failure mode of small depressions in the shell plate between ribs of stiffened conical shell structure was obtained, that was, independent small pits were formed along the axis direction. According to the theory of elastic-plastic deformation of plate and shell structure, the small pits of shell and plate between ribs were approximated as the deformation of trapezoidal plate, and the deformation function of trapezoidal plate was obtained by coordinate transformation. The deformation energy of plate and shell was divided into bending deformation energy and midplane strain energy. By establishing the correlation between explosion energy and deformation energy, the theoretical calculation model of the small pit deformation mode of shell and plate between ribs was obtained. [ABSTRACT FROM AUTHOR]

• Development of a finite element formula in Total Lagrangian framework for large deformation of isotropic and anisotropic membrane structures without restriction to geometry, loading and boundary conditions. • Representation of both invariant-based and stretch-based strain energy density functions, and derivation of actual values of fourth-order elasticity tensor dealing with the complexities of transformation between Cartesian and principal coordinates for stretch-based strain energy density functions. • Employing the exact form of the fourth-order elasticity tensor in finite element method for stretch-based hyperelastic material model. • A comparative study between deformations in terms of invariant-based and stretch-based formulations in possible cases. A nonlinear finite element formulation for large deformation analysis of hyperelastic membranes in Total Lagrangian framework is developed. In many cases, it is convenient to utilize the invariant-based strain energy density function to analyze the structures when employing the finite element method. However, in this contribution, both invariant-based and stretch-based formulations are developed. Formulations are completely general and not restricted to axisymmetric loading and geometry of membrane. Furthermore, initially flat and non-flat membrane can be investigated by this method. Incompressible as well as compressible materials can be modeled. A method for imposing the plane stress condition to the formulation for compressible materials is presented. Moreover, isotropic and anisotropic materials can be considered. Some problems are analyzed and results compared to the available ones in the literature. The comparison between solution based on invariant-based method and stretch-based method with exact fourth-order elasticity tensor obtained in this work demonstrates that the stretch-based method derived in this paper works very well. The presented examples demonstrate that the developed formulations have no restriction or simplification with respect to the modeled object geometry and inherent anisotropy. [ABSTRACT FROM AUTHOR]

• A 3D free-bending process method that can accurately control the process parameters in transition zone is proposed. • An analytical model of finned special-shaped tube bending forming based on exponential hardening behavior is constructed. • The influence rule of the speed parameters in transition section on the forming radius and cross-section deformation is obtained. • FE results are in good agreement with experimental results. In 3D free-bending technology, the bending forming of the tube consists of the transition section and the stable forming section. However, because of the continuous movement of the bending die and tube in the transition section, the forming mechanism of the tube in the transition zone is relatively complex and still unclear. In addition, due to the complexity of the cross-section deformation of the finned special-shaped tube (FSST), its application in the heat dissipation pipeline of aerospace vehicles is severely hindered. To address the above issues, in this paper, a 3D free-bending forming process method, which can effectively coordinate the movement of FSST and the bending die in the transition section, was proposed. Meanwhile, an analytical model of FSST bending forming was established, which can effectively characterize the elastic-plastic evolution of the FSST cross-section and match the bending radius with the cross-sectional bending moment effectively. Then, the effectiveness of the process method and analytical model was verified by finite element model (FEM), and experiments. Further, FEM and experiments were used to investigate the influence of the process parameters of the transition section on the forming radius and cross-section deformation of FSST after springback. The results from this study show that reasonable coordination of the rotation speed of the bending die and the advancing speed of FSST in the transition zone can improve the forming quality of FSST. [ABSTRACT FROM AUTHOR]

As a typical hybrid lattice, vertical-reinforced lattices, i.e., adding vertical struts to traditional lattices, have not been extensively studied, especially from the aspects of deformation mechanism, energy absorption performance and structural optimization. In this paper, body-centered cubic (BCC), face-centered cubic (FCC), as well as vertical-reinforced BCC and FCC (VBCC and VFCC) lattices were established and fabricated by the selective laser melting technique to elucidate the influence of the vertical struts on the mechanical behavior of the lattices. Uniaxial quasi-static compression tests were conducted on lattice samples made of stainless steel 316L. Moreover, numerical simulations were performed to facilitate analysis of the deformation modes of the specimens and further optimization designs. The results show that the VBCC and VFCC lattices exhibit stronger stiffness and higher initial strength compared to the BCC and FCC lattices. Typically, the effective specific energy absorption of the vertical-reinforced lattices can be increased by about 60%–75% compared with those of non-reinforced lattices, since more plastic hinges are formed in the lattice via adding vertical struts to dissipate energy. The present study also demonstrates that increasing the diameter of the vertical struts plays a vital role in improving energy absorption capabilities of the vertical-reinforced lattice, and the highest effective specific energy absorption of optimized VBCC and VFCC lattices are 21.7 J/g and 27.9 J/g, notably far above the general trend of most metal lattices. • Vertical-reinforced lattices exhibit excellent energy absorption performance. • Mesoscopic deformation mechanisms of vertical-reinforced lattices are elucidated. • A theoretical model of plateau stress is proposed for vertical-reinforced lattices. • Energy absorption regulation of vertical-reinforced lattice through optimal design. [ABSTRACT FROM AUTHOR]

Highly flexible thin-walled beams with complex open cross-sections are sensitive to torsional and warping effects. The analysis of higher-order vibration modes in these structures needs more accurate and precise methods in order to achieve reliable results and detect the cross-sectional deformations in the structures' free vibration response. This paper analyzes higher vibration modes in a series of thin-walled beams, which were proposed by Chen as benchmark problems. These are all open-section thin-walled beams with complex geometries. Global vibration modes, such as bending and torsion, related to the rigid cross-sectional deformations can be detected via classical and shear refined theories. However, cross-sectional deformations appear at higher frequencies, and these modes are mixed with the global ones. To highlight this fact, this paper compares classical beam theories with refined ones based on the Carrera Unified Formulation (CUF) and the shell results using the commercial finite element (FE) software and the data available from the literature. The CUF FEs based on the power of cross-sectional deformation coordinates (x, z) and those based on the Lagrangian polynomials are implemented and compared using Modal Assurance Criterion. A number of interesting conclusions are drawn about the effectiveness of classical and CUF-based results. The need for models capable of detecting cross-sectional deformations is outlined. In fact, many modes are lost by classical beam theories; on the other hand, they show rigid cross-section modes that do not really exist. This fact is also confirmed by the shell models, which are more expensive in terms of computational costs regarding the efficient CUF ones proposed here. [ABSTRACT FROM AUTHOR]

Shot peening is an essential process for forming large thin-walled components in aerospace industries. However, it is challenging to determine directly the mapping relationship between shot peening parameters and deformation response because of the complex elastic–plastic deformation of shot-peened components. In this paper, a computational model of bending deformation of peened plate samples is established by examining the shot peening behavior from the aspect of energy equivalence, in which the deformation energy of the shot-peened plate is determined by the total kinetic energy input due to the shot impacts and a correction factor that takes into account the influences of oblique impact, shot interaction and shot overlap on the peen forming process in practice. It is proven that the square of curvature radius is proportional to the cube of the thickness but inversely proportional to the indentation coverage and the average kinetic energy input of a single shot. For the effect of a single shot impact in peen forming, the average kinetic energy input of a single shot is a power function with the indentation diameter. • Deformation of peened plate is explained from the aspect of energy equivalence. • The square of curvature radius is proportional to the cube of the thickness. • The square of curvature radius is inversely proportional to the coverage. • The square of curvature radius is inversely proportional to the kinetic energy. • Kinetic energy input is a power function with the indentation diameter. [ABSTRACT FROM AUTHOR]

The aim of this paper is to develop two novel in-plane auxetic structures with remarkable stiffness and negative Poisson's ratio (NPR) appropriate for compression and tensile load-bearing structures. The combination of re-entrant and arrow-head (RAH) unit-cells as well as star and arrow-head (SAH) unit-cells are hybridized and configured as new auxetic structures. The conceptual design is based on the stretch-dominated-mechanism (SDM) deformation of the proposed structures. To investigate the mechanical behavior of the designed structures under compressive and tensile loading, the samples are manufactured by 3D fused deposition modeling printing method and subjected to mechanical testing. The results show that the designed structures present tunable NPRs and approximately equal stiffnesses for both compressive and tensile loadings. In addition, an analytical analysis is carried out to determine the elastic constants of the structures, and a finite element (FE) simulation is conducted to verify the results with experimental and theoretical models. Good agreements are found for the elastic constants calculated from the experimental, theoretical, and FE methods. Meanwhile, the effects of the geometry parameters on the mechanical properties of the designed structures are also investigated, and the stiffness, stiffness to relative density ratio, and NPR are compared with those of existing studies. The comparison results suggest that our developed structures can be considered as strong candidates for the next generation of SDM auxetic structures with high stiffness capability and noticeable NPR values. [Display omitted] • Novel auxetic structures are designed based on the stretch-dominated-mechanism. • The designed structures demonstrate the close stiffness under compressive and tensile loadings. • The designed structures have enhanced stiffness and negative Poisson's ratio values, simultaneously. [ABSTRACT FROM AUTHOR]

Traditional auxetic metamaterials are characterized by negative Poisson's ratio but weak stiffness. In this paper, a new auxetic metamaterial, re-entrant star-shape anti-chiral auxetic metamaterial (Re-S-AC), is proposed and the in-plane mechanical properties of the Re-S-AC are investigated by experimental test and numerical analysis. The crushing test of the Re-S-AC fabricated by the selective laser melting (SLM) method is performed to investigate the deformation mechanism and validate the accuracy of the numerical model. Compared with the anti-tetrachiral and re-entrant star-shape, the Re-S-AC simultaneously exhibits concave and rotational deformation under the in-plane compression, and mean compression stress is highest at the same thickness and same mass. In addition, parametric analysis is conducted to comprehensively reveal the influence of geometric characteristics on the mechanical properties of the Re-S-AC. The results found that the node center distance, node diameter and wall thickness have significant effect on the mechanical properties and deformation mode of the Re-S-AC. Compared with other parameters, wall thickness has the greater effect on the mechanical properties. When wall thickness is from 0.4 mm to 0.8 mm, the Young's modulus, yield strength, and mean compression stress increase by 447.27%, 530.62%, and 370.87%, respectively. This study provides a reference method for improving the mechanical properties of the auxetic metamaterial. • A new auxetic metamaterial (Re-S-AC) is proposed by coupling concave-rotation deformation. • The deformation mechanism of the Re-S-AC is explored by quasi-static crushing experiment. • The Re-S-AC has better mean compression stress than the anti-tetrachiral and re-entrant starshape metamaterial. • Parametric analysis is conducted to reveal the influence of geometric parameters on the mechanical properties. [ABSTRACT FROM AUTHOR]

Confining with an outer sleeve is an effective means of enhancing the load-bearing and deformation capacity of compression struts. The outer sleeve and compression strut, i.e., inner core, constitute a sleeved core-loaded member, where the latter ideally bears all the axial compression under the lateral restraint of the former. Additionally, an extension segment of the inner core is typically required as the allowance for contraction. However, the unrestrained extension segment is prone to excess flexural deformation, dramatically decreasing the overall load carrying capacity of the sleeved member. In this paper, first, an analytical investigation of the behaviour of the sleeved member with pinned ends is presented. Second, a numerical study was conducted to determine the limit state of the localized flexural failure and to propose the corresponding design criterion combining the analytical model. Last, the design criterion was further validated by compressive tests, indicating that the proposed method accurately predicted the localized​ flexural failure of both seamless-sleeved members and members with assembled outer sleeves. • A theoretical model on the localized flexural failure of sleeved members is built up. • The corresponding design criterion is proposed combining numerical cases. • The unrestrained length ratio of the core and the gap width exhibit notable effects. • The theory is validated by tests on both seamless- and assembled-sleeved members. [ABSTRACT FROM AUTHOR]

Generalised Beam Theory assumes the displacement field of a thin-walled member as a linear combination of deformation modes. The main family of deformation modes is constructed based on two simplifying assumptions: null membrane shear strain and null membrane transverse extension. If these modes are not sufficient for an accurate representation of the structural behaviour, two other families of modes are derived (from the main family) for which the two simplifying assumptions are eliminated. In this paper, for the special case of thin-walled cylinders, all three families of deformation modes are replaced by a new unified family, for which the membrane shear strain and transverse extension are not neglected. The derivation of the proposed modes is based on the stress equilibrium equations, and it involves the trigonometric series representation of the longitudinal modal amplitudes. The advantages of the proposed modes are highlighted throughout several linear buckling analyses with various loading and boundary conditions. • New GBT deformation modes are derived using the stress equilibrium equations. • Longitudinal modal amplitude functions are represented by trigonometric series. • Stiffness matrices are derived for linear buckling analysis. • Formulation is validated using shell finite element models. • Proposed formulation is compared with classical GBT. [ABSTRACT FROM AUTHOR]

When materials are in tension or in compression, their mechanical properties are essentially different, however, in existing studies it is generally ignored because of the complexity of the analysis. In this paper, a theoretical study of the problem of axisymmetric large deformation of thin shallow shells with different moduli in tension and compression (bimodular thin shallow shells) under uniformly vertical loading is presented. Based on the Föppl–von Kármán equations of flexible thin plates, the governing equation of the axisymmetric large deformation of bimodular thin shallow shells are established by introducing an appropriate curvature modification term from thin shallow shells and a bending stiffness term from bimodular plates. By selecting the central deflection as a perturbation parameter, the perturbation solution of the axisymmetric large deformation problem is derived using the perturbation method. The applications of variation method as well as the implementation of numerical simulation verify, from the theoretical and numerical perspectives, the correctness of the perturbation solution obtained. This study shows that the introduction of different moduli in tension and compression not only affects the relationship of loads vs. central deflection, but also affects the critical values of the rise-thickness ratio of bimodular thin shallow shells when the snapping phenomenon occurs. In particular, the bimodular effect may accelerate or slow down the occurrence of the snapping phenomenon of thin shallow spherical shells, according to the relative magnitude of tensile and compressive moduli. The work presented here will be helpful to analyze the mechanical response of heavily loaded thin shallow shells with obvious bimodular effect. • A set of governing equation for bimodular thin shallow shells is first established. • The perturbation method is first used to solve the governing equations. • The variation method and numerical simulation validate the perturbation solution. • The bimodular effect will influence the relationship of loads vs. central deflection. • The bimodular effect will accelerate or slow down the snapping phenomenon. [ABSTRACT FROM AUTHOR]

A new type of braced frame structure with a double-cylinder arc energy dissipator is proposed in this paper. The energy dissipator is composed of an inner cylinder, an outer cylinder, and a stiffener fabricated and connected to a steel beam and column by welding, and the double cylinder arc energy dissipator is connected to a steel beam and steel column by welding. The seismic performance of the braced frame structure with a double-cylinder arc energy dissipator was analyzed by Abaqus. The results indicated that seismic energy could be dissipated through the deformation of the outer cylinder, inner cylinder, and rib plate. However, the double-cylinder arc energy dissipator could avoid the out-of-plane buckling deformation of the brace. Further, it exhibited properties similar to those of concentrically and eccentrically braced frames. The deformation of the braced frame with a double-cylinder arc energy dissipator mainly occurred on the dissipator and energy-dissipating beam (between the dissipator and column). During the loading process, the stiffener, outer and inner cylinders, and beam gradually yield. The height, thickness, and spacing of the stiffener of the double-cylinder arc energy dissipator were observed to significantly influence the seismic performance of the proposed braced frame. In contrast, the effect of the thicknesses of the inner and outer cylinder arcs on performance was negligible. • Seismic performance of braced frame structure with double cylinder arc energy dissipation was studied. • The initial stiffness, linear stiffness, and bearing capacity of the structures under monotonic load were studied. • Energy dissipation capacity, degradation property, failure, and deformation modes under low-cyclic loading were studied. [ABSTRACT FROM AUTHOR]

In this paper, an anti-buckling fixture was proposed to assess the deformation characteristics of DP500 and DP980 dual-phase steels, and AZ31B magnesium composite under tension–compression cyclic loading. The advantage of the device lies in the possibility of monitoring friction between the specimen and supporting blocks during the test. In consequence, it allows to avoid an error during stress determination. The full cyclic loading capacity for each material can be executed at the displacement amplitude within the range ± 2.5 mm which corresponds to the maximum strain amplitude of ± 0.2 for the specimen with the gauge length of 21.5 mm. It is concluded, that the technique proposed is promising since the thin sheet material can be tested under tension–compression in a wide range of deformation without the buckling effect. Furthermore, useful data for modelling cyclic deformation behaviour for shell structures can be obtained. [Display omitted] • Proposed fixture enables to avoid buckling during thin metal sheet compression. • The friction force is continuously registered during the test. • Complex characteristics could be successfully and precisely determined. • Useful data for modelling cyclic deformation can be obtained. [ABSTRACT FROM AUTHOR]

Due to lack of effective backup when drilling aircraft thin-walled CFRP structure, serious dynamic structural deformation including vertical and in-plane deformation usually occur, which extremely changes the cutting behavior and materials removed mechanism, causing severe entrance and exit damages. Therefore, this paper proposed a dynamic deformation measurement experiment in vertical and horizontal direction at various processing parameters to analyze their effects on cutting mechanism and damages distribution. Results show the vertical and in-plane deformation occurrence are highly dependent on the actual positions of tool-CFRP system. Namely elastic deformation, local deformation and drawback reflection appear many a time in different stages, causing obvious sudden change of thrust force and different initiation and propagation characteristics of damages. With the feed rate increasing and workpiece thickness decreasing, the maximum displacements of every stages all increase and some thinner workpiece displacement exceed several times the plate thickness. The larger in-plane deformation will nonuniformly distribute along borehole exit due to the different cutting mechanism and strength of different fiber cutting angles. The larger elastic deformation and drawback action in vertical direction will change the out-ply material remove mechanism into mainly puncture rather than only cutting. Under the joint action of deformation in two directions, the loose surface damages composed of delamination and uncut fiber will gather heavily at exit. • The vertical and in-plane deformation were characterized in divided stages by DIC. • The influence of drilling parameters on deformation and drawback was investigated. • The cutting behavior at various FCA under large drawback action was revealed. • The damage formation and propagation mechanism of drilling process was analyzed. • The in-plane damages in entrance and exit regions after deformation were evaluated. [ABSTRACT FROM AUTHOR]

Curved tubes are widely used on autobody to suffer the transverse bending loads. This paper studies the energy absorption performance of curved tubes under transverse bending load. Firstly, three-point-bending and fully clamped bending experiments are conducted for three kinds of curved tubes with different radii. It is found that the curvature has a significant impact on the energy absorption effect under the fully clamped condition. However, the influence is limited and it will be easily ignored in the three-point-bending condition. Under fully clamped condition, tubes with large radii have three-plastic-hinges, and curved tubes with small radius have five-plastic-hinges. Due to the participation of axial force, the energy absorption of the curved tubes under fully clamped condition is 2.8–4.1 times that of the three-point-bending condition. Subsequently, FE models of curved tubes with different radii are established to analyze the effect of curvature on the deformation mechanism and energy absorption. It is found that whether the shortening of the plastic hinges can meet the requirements of geometric compatibility determines the deformation modes of curved tubes. The influence of loading (loading direction) and geometric (cross-section and thickness) factors are also discussed. Finally, a theoretical model of curved tubes with three-plastic-hinges mode is proposed to predict the energy absorption performance. • Three-point-bending experiments and fully clamped bending experiments are conducted on curved tubes. • FE models of curved tubes are established and verified by experimental results. • How the curvature influences the energy absorption mechanism of tubes under transverse loading is presented. • The effects of loading direction, cross-section and thickness on curved tubes are discussed. • Theoretical analysis is conducted on curved tubes with three-plastic-hinges mode under fully clamped condition. [ABSTRACT FROM AUTHOR]

This paper presents a new deformation assisted joining process for connecting tubes to stronger tubesheets, which involves reduction of the free tube end by local indentation of the tubesheet and subsequent flaring against the tubesheet surface to create a mechanical interlocking. The methodology draws from the fundamentals of the new proposed process to the identification of the major variables and their influence on the overall deformation mechanics. The work combines experimentation and numerical simulation with finite elements and is carried out in unit cells consisting of a polymer tube and a metallic sheet with a drilled hole that are representative of the tube-to-tubesheet connections of heat exchangers. It is shown that the new deformation assisted joining process can produce tube-to-tubesheet connections in which the tubes are softer than the tubesheets, paving the way for manufacturers of heat exchangers to combine polymer tubes with metallic tubesheets (and shells) in applications where the media running inside the tubes is incompatible with the use of metallic tubes in long service life. In addition to the originality resulting from the new polymer-metal tube-to-tubesheet connections, the new proposed deformation assisted joining process is also the first ever in its category to make use of tube reduction, instead of tube expansion, to produce these types of joints. • Innovative deformation assisted joining process for connecting tubes to stronger tubesheets. • First time ever application of tube reduction to produce tube-to-tubesheet joints. • Fostering new heat exchanger designs that make use of polymer tubes and metallic tube sheets and shells. • Numerical and experimental investigation on unit cells to demonstrate the process applicability. • Destructive pull-out tests to evaluate the force to detach the tubes from the tubesheets. [ABSTRACT FROM AUTHOR]

In this paper, the plastic behavior of a fully clamped sandwich beam with fiber metal laminate (FML) face-sheets and metal foam core under transverse loading is analytically and numerically studied. Based on the modified rigid plastic model, the analytical solution for large deflection of FML sandwich beams under transverse loading is given, in which the local denting deformation is considered. Finite element results are conducted, and analytical solutions capture numerical results reasonably. The influences of material and geometrical parameters on the plastic behavior of FML sandwich beams are considered. The results show that the present analytical model can be used to predict the plastic behavior of fully clamped FML sandwich beams considering the local denting deformation. • Plastic behavior of sandwich beams with fiber metal laminate (FML) face-sheets is studied. • A simplified formula for plastic behavior of FML sandwich beams is obtained considering local denting. • Analytical solutions capture numerical results reasonably. [ABSTRACT FROM AUTHOR]

With the increasing requirements on the parallelism and flatness of thin-walled flat parts, vacuum fixtures have been widely used in precision manufacturing. While several research studies focus on using the finite element method to predict the clamping deformation in the vacuum clamping system, it is very time-consuming and often unable to obtain the convergent solution with complex boundary conditions. In this paper, based on Kirchhoff plate theory, a new method was proposed to solve the clamping deformation of the thin circular workpiece with various complex boundary conditions subjected to vacuum negative pressure. The improved Rayleigh–Ritz method was applied to solve the spatial partial derivatives. The admissible function was composed of polynomial and trigonometric functions, which explained the unconstrained state of the workpiece. Furthermore, Courant's penalty method was used to handle the constraint conditions. Simulations and experiments were conducted to verify the convergence, feasibility, accuracy, and applicability of the proposed method. The results showed that the proposed method is well-suited for arbitrary boundary conditions with vacuum fixture system, and its convergence was good compared to the finite element method. Finally, the influence factors of clamping deformation were discussed comprehensively and were optimized to reduce the clamping deformation. The proposed method can quickly calculate the clamping deformation of the thin circular workpiece under different vacuum clamping conditions, which provides the guidance for fixture design and the selection of clamping parameters for researchers in the processing field. • The energy equation of the thin circular plates under vacuum clamping loads is developed. • The improved Rayleigh–Ritz method associated with Courant's penalty method are used to solve the clamping deformation with complex conditions. • The influence factors of clamping deformation are comprehensively analyzed. • An optimization model of the vacuum fixture is established. [ABSTRACT FROM AUTHOR]

Limited studies were reported about energy absorption characteristics of combined honeycombs subjected to uniformly distributed explosive loading in air. In this paper, the cutting strain of the combined honeycomb core considering the effects of core diameter, explosive charge mass and scaled distance was first investigated through air explosion experiments. A full-scale finite element (FE) model and a homogenization method were then proposed and verified by comparing the numerical solutions with the experimental results. Based on the FE model, the individual effects of the peak overpressure and positive impulse on the cutting performance were revealed. The experimental results demonstrated that either a decreasing scaled distance or an increasing charge mass resulted in a larger cutting strain. The numerical solutions indicated that similar changing tendencies to cutting strain were observed for the cutting plateau stress and energy absorbed by the combined honeycomb. Based on the dimensional analyses, a semi-empirical formula was proposed for predicting the relationship between the absorbed energy and cutting plateau stress. In addition, a deformation mode map was developed. The map plotted the peak overpressure vs. the impulse and identified the dominant deformation mode for each application point in this space. The map can be used in combination with the semi-empirical formula, and then the cutting performance of the combined honeycomb can be determined easily and quickly. • The homogenization method of DLCHs under explosive loading was established, and had been verified by experimental results. • A semi-empirical formula was proposed for predicting the relationship between the absorbed energy and cutting plateau stress. • A deformation mode map was developed which identified the dominant deformation mode in P-I coordinates. [ABSTRACT FROM AUTHOR]

This paper proposes a procedure to calculate cross-section deformation modes for steel–concrete composite bridge cross-sections, including shear connection flexibility, within the framework of the Generalized Beam Theory (GBT). The proposed procedure is computationally efficient and makes it possible to (i) handle arbitrary (flat-walled) composite cross-sections, including complex configurations with several closed cells, (ii) consider the geometric offset between the steel and concrete mid-lines, which is essential in steel–concrete composite members, and (iii) automatically identify, separate, and hierarchize the deformation modes into physically meaningful sets, including a set of shear connection slip deformation modes. For illustrative purposes, the various deformation mode sets are determined for two representative cross-sections, namely a twin-girder and a box-girder with closed longitudinal stiffeners. These deformation modes are then employed to perform the structural analysis of simply supported decks, showing that very accurate results are obtained with a small number of deformation modes and that the modal decomposition of the solution provides in-depth insight regarding the bridge structural behavior. • A method for calculating the GBT deformation modes for steel–concrete bridges is developed. • Complex longitudinal stiffeners can be easily handled. • Shear connection stiffness is taken into account. • The resulting GBT-based finite element is very accurate and efficient. [ABSTRACT FROM AUTHOR]

A corrugated sandwich panel consists of two face-sheets and a corrugated core, which is made of sheets that are folded into a corrugated shape. In this paper, the mechanical response of aluminium corrugated sandwich panels subjected to longitudinal loading along its middle line is investigated experimentally, numerically, and theoretically. A parametric study is conducted using ABAQUS/Explicit to examine the effects of geometric configurations (i.e., corrugation angle, core height, and core web thickness) on the deformation mode, peak force, and specific energy absorption (SEA) of panels. Two major deformation modes (Mode I and Mode II) are observed. The sandwich panels that deformed in Mode I has higher peak force and energy absorption ability. When the density of core remains the same, the energy dissipated by sandwich panels can be tailored by varying the geometry of the core. Thicker core webs result in greater energy absorption. Based on the experimental and simulation observations, a theoretical analysis using energy method is carried out to predict the crushing force of panels during large deformation. • The large deformation of corrugated sandwich panels under longitudinal bending was investigated. • A parametric study was conducted using ABAQUS/Explicit. • Theoretical analysis of the crushing force based on energy method was carried out. [ABSTRACT FROM AUTHOR]

In this paper, a concave-shaped unit composed of two thin-walled beams with cantilever boundary conditions is designed and fabricated. Forces are introduced through the two cantilever ends of the beams whose constraints are hinged joints to get a bi-stable axial or lateral buckled unit. Initial buckling deformations of the concave-shaped units are analyzed theoretically and numerically. Experimental and numerical methods are used to investigate the post-buckling deformations and snap-through behaviors, when the concave-shaped units are axial buckled or lateral buckled. In the case of completing downwards and upwards snapping processes, there is a hysteresis loop in the force–displacement curve for the bi-stable lateral buckled unit, while is not for the bi-stable axial buckled unit. Finally, the influence of transverse displacements and dimension parameters on the snap-through behaviors of the bi-stable lateral buckled units is studied by the simulation method. • A bi-stable lateral buckled unit is designed and fabricated. • There are two symmetric modes for the initial buckled concave-shaped unit. • Post-buckling and snap-through behaviors of the bi-stable units are investigated. • The energy dissipation capacities are influenced by beams parameters. • The assembly bi-stable units are good candidates for energy-related applications. [ABSTRACT FROM AUTHOR]

This paper presents a general post-processing procedure that enables retrieving GBT deformation mode amplitudes directly from shell finite element or finite strip results with a small computational cost. The procedure extends that for proposed in Cai (2019), in the context of bifurcation analyses, to all deformation mode families (conventional, shear and transverse extension), several analysis types (first-order elastic/elastoplastic and vibration) and problems with complex geometry (e.g., tapered or curved parts), which are difficult to analyse or cannot be analysed with GBT. Therefore, the unique GBT modal decomposition features, making it possible to acquire in-depth insight into the underlying mechanics, can be used even in complex problems. In order to demonstrate the accuracy of the proposed procedure, several validation examples are presented, involving problems for which "pure" GBT analyses can be performed. Finally, a set of application examples are provided, to show the capabilities and potential of this new approach. • GBT deformation modes are retrieved from shell FE and finite strip results. • The procedure can be employed when standard GBT analyses are not possible. • The procedure can be also used when standard GBT is not computationally efficient. • The GBT modal decomposition in tapered/plastic/curved members is easily obtained. [ABSTRACT FROM AUTHOR]