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Mechanical metamaterials are valued for their diverse properties and potential applications. Due to the instability and large deformability of soft mechanical metamaterials (SMMs), geometric reorganization will occur and lead to some unusual properties. It is possible to change the properties of materials by varying the parameters. Conventional SMMs contain a periodic distribution of holes with the same size and shape, which can be changed to a lesser extent. Periodic dispersion of regular through-hole patterns of various sizes or shapes into elastomers, resulting in metamaterials with more mechanical functionality and deformation scenarios. In this paper, we investigated the influence of parameters on the buckling mechanical behavior of SMMs and the buckling mechanical behavior of structures with multiple sizes and geometric shapes. The parameters studied include geometric parameters (pore shape, porosity and area ratio) and physical parameters (Poisson's ratio and compression mode). Simulation of the buckling behavior of SMMs uses the finite element method. The finite element software ABAQUS is used, taking into account the almost incompressible characteristics of materials, the triangular quadratic plane strain hybrid element is selected (CPE6H). Numerical calculation gives the following results: Area ratio, pore shape and compression mode have obvious effects on buckling behavior, but Poisson's ratio has little effect; the influence of parameters on the buckling critical strains varied for SMMs with various pore shapes; very different buckling behaviors will result from swapping out the pattern of holes with the same size or shape for holes with two different sizes or shapes; the expression of buckling behavior is also varied when the mix of hole shapes is modified. These findings demonstrate that the design parameters may be used to achieve the desired buckling behaviors. This is a new method that can be used to control the deformation of structures; modify the properties of the SMMs without changing stiffness; simplify the structures without significantly changing the material properties. The design path of mechanical metamaterials is increased. [ABSTRACT FROM AUTHOR]

A steel brace is effective to retrofit old reinforcement concrete (RC) buildings by increasing the horizontal load capacity of structures. However, concrete cracks that easily occur in the surrounding RC members under tension initiate early strength degradation, so this research aimed to develop a new self-centering brace (SCB) with the compression-only capacity such that no tension force is developed in the brace or to the adjoining RC members. Original SCBs have been developed to reduce the residual deformation of structures with a symmetrically flag-shaped hysteretic response. By altering the force transfer mechanism in the original SCB, a compression-only self-centering brace (C-SCB) can be developed under a symmetrically reversed cyclic loading, providing an alternative for the RC building retrofit. This paper first introduces the mechanics and deformation mechanism of the proposed C-SCB. A test program is then conducted on the cyclic tests of a buckling-restrained energy dissipating bar (EDB) to evaluate the energy dissipation. A 3,695-mm-long C-SCB is composed of posttensioning high-strength steel tendons, steel compression members, and buckling-restrained EDBs for the energy dissipation. The C-SCB in tests showed a good compression-only self-centering capability up to an axial displacement of 31 mm, with a maximum axial force of 1,530 kN. No damage of the steel tendons, compression members, or EDBs was found after three phase tests. Finite element analysis further validated the compression-only hysteretic response and mechanics of the C-SCB in a symmetrically reversed cyclic loading. [ABSTRACT FROM AUTHOR]

In the present paper, the effect of aspect ratio on the initial buckling response of an elastically supported rectangular FGM plate, the thin plate spline radial basis function (RBF) method can be used. This method involves the use of a thin plate spline to interpolate the displacement field of the plate, allowing for accurate analysis of the plate's behavior. The higher-order shear deformation theory (HSDT) is used for the analysis of the FGM rectangular plate resting on two parameters of elastic foundation. The displacement field consists of five unknown variables and approximately parabolic distribution of the transverse stress profile through the plate thickness and tangential stress-free boundary conditions on the plate surface. The governing differential equations (GDEs) of the plate are developed in the framework of Hamilton's principle. The thin plate spline radial basic function-based Meshfree method is used for discretizing the GDEs. To demonstrate the accuracy and efficacy of the present approach, the results obtained by the present approach are compared with the results given in the literature. The effect of various aspect ratios, grading index, span-to-thickness ratio, and two parameters of elastic foundations on the normalized buckling load is proposed. Some new results are also presented, which may be beneficial for future research works. The novelty of the present is the effects of aspect ratio on the elastically supported FGM plates. [ABSTRACT FROM AUTHOR]

In the process of horizontal well construction, the working environment in the well is very complicated. It is difficult to determine the actual deformation and force of the coiled tubing in the wellbore from the load change at the wellhead along. In addition, the coiled tubing wrapped around the reel and entering the wellbore through the injection head may cause an initial residual bending. In this paper, the mathematical model of the coiled tubing under axial load during buckling deformation is established, and the analytical solution with the time term is derived by reasonable simplification of the model. The effect of residual bending on the post-sinusoidal buckling of the coiled tubing in the horizontal well was investigated using the separation variable method. The effect of residual bending variations on the well wall contact forces is analyzed. The research shows that the initial parameter Г is the main factor influencing the post-sinusoidal buckling of the coiled tubing with residual bending. The larger the parameter value Г, the greater the effect of the residual bending on the post-sinusoidal buckling deformation of the coiled tubing, and the earlier the critical point of the mixed sinusoidal-helical buckling of the coiled tubing appears. The compression velocity of the coiled tubing has a significant effect on the well wall contact force. The faster the compression, the greater the contact force. By introducing the time term and the separation variable, this paper provides a new method and theoretical basis for further study of the process of entering sinusoidal-helical buckling of the coiled tubing with initial residual bending. [ABSTRACT FROM AUTHOR]

Buckling of axially loaded beams is discussed in the context of Λ-fractional analysis and mechanics. An axially compressed cantilever beam is considered in the Λ-fractional space, and the critical load is defined. The variational buckling problem of the simply supported beam is considered in the Λ-fractional space. It is pointed out that the Euler–Lagrange equation corresponding to the minimization of the total energy function with the Weierstrass–Erdmann conditions is only acceptable. The Λ-fractional buckling elastic curve of a simply supported beam is presented. That elastic curve is transferred into the initial space. The post-critical buckling deformations are defined in the context of globally stable equilibrium deformations. [ABSTRACT FROM AUTHOR]

A full-scale, two-tiered steel buckling-restrained braced frame (BRBF) was tested to evaluate experimentally the seismic behavior of steel multitiered BRBFs, namely, column stability response, column seismic demands, and tier deformations under a loading protocol representing earthquake ground motions. The test specimen consisted of diagonal braces oriented in opposing directions in the two adjacent tiers to create the most critical multitier response. The test frame was designed in accordance with the 2010 AISC Seismic Provisions as a lateral load-resisting system of a single-story building. The frame was subjected to a three-phase loading protocol consisting of lateral displacement time histories corresponding to a far-field ground motion record and a near-field ground motion record applied sequentially achieving total frame drifts in excess of 3.5%, followed by a final monotonic lateral displacement corresponding to 4.5% story drift. The test frame exhibited a stable response despite a non-uniform distribution of frame inelastic deformation between the tiers, which induced significant in-plane bending moments in the columns. Flexural bending, combined with a large axial compression force, led to partial yielding in the columns. Large deformation demands were also observed in the BRB yielding in tension and attracting the majority of frame lateral deformation. On the basis of test results, a displacement-based analysis approach was proposed to relate column in-plane bending and flexural stiffness to relative inelastic tier deformations. [ABSTRACT FROM AUTHOR]

This paper presents a theory for the buckling of short beams considering cross-sectional distortions due to transverse shear (i.e., shear warping), based on the consistent linearization of a geometrically nonlinear planar beam. The proposed deformation field considers the warping amplitude as an independent kinematic field, and the hyperelastic material assumes that the stresses normal and tangent to the deformed cross section are linear with respect to their work-conjugate finite strains. An approximate closed-form solution to the resulting quartic equation for the critical load is provided to facilitate practical implementation. Theoretical differences giving rise to distinct buckling theories for higher-order shear beams are discussed in terms of (1) the assumed deformation field, (2) variational consistency, and (3) material constitutive relation. The proposed formulation is applied to evaluate the stability of infinite strip unbonded fiber-reinforced elastomeric isolators (FREIs) with moderate-to-high shape factor, for which shear warping is expected to have a major influence due to the flexural flexibility of the fiber reinforcement. A homogenization procedure is described to obtain effective isolator rigidities considering rubber compressibility and fiber extensibility. Next, a finite element parametric study of the buckling of unbonded infinite strip FREIs is presented, and the results are used as a benchmark to evaluate the adequacy of the proposed and existing formulations. The theory presented herein and its approximate solution exhibit the best match with the numerical results, and the latter is deemed adequate for practical application. [ABSTRACT FROM AUTHOR]

The moving deformation of the strata and the redistribution of stope stress after mining show asymmetrical characteristics, which do not conform to the symmetrical structural characteristics of the original rock beam fracture. To further analyze the deformation of rock beams and the asymmetry law of stope pressure distribution after strata caving, the detailed process of instability and deformation of composite rock beams before failure was revealed through similar material simulation, theoretical analysis, and numerical simulation. Through similar simulation experiments, the structural characteristics of strata caving were observed. After excavation, the caving angle near the open-off cut side of the model is greater than that on the stop-mining line side. The maximum bending moment of the rock beam is located at the open-off cut side. The rock beam fracture is located on the partial open-off cut side in the middle of the rock beam. The rock beam on the open-off cut side is easy to shear slip and not easy to hinge. The rock beam in front of the advancing direction of the working face is easily hinged. Based on the structural characteristics of strata caving, considering the thickness of the composite rock beam, the two-hinged arch mechanical model for rock beam fracture is established. On this basis, the key parameters of rock beam instability and fracture such as limit load, additional horizontal stress, limit break distance, and break position are analyzed. Based on the deformation characteristics of two hinged arches, the caving structure and the asymmetric distribution mechanism of stress redistribution during the deformation of overburden in stope are explained. Finally, the deformation of rock beam and the asymmetry of stress distribution in stope are verified by numerical calculation. The results show that the concentrated stress value of the coal pillar at the open-off cut side is greater than that in front of the working face. There is a pressure relief area behind the working face, and the pressure relief area has a certain range. The range of stress concentration area, pressure relief area, and stress value tend to be stable, and only the range of the original rock stress zone expands when the working face is advanced to a certain distance. The asymmetric distribution of compaction stress in goaf is related to the buckling deformation of strata. [ABSTRACT FROM AUTHOR]

Buckling phenomenon is a common failure mode for composite materials under the effect of compressive loading which is mainly investigated in two stages as pre – buckling and post – buckling. At the pre – buckling phase, the deformations take place temporarily in elastic range. However, load carrying capacity of a member can be increased by regarding the post – buckling process. Therefore, it is important to determine the final and maximum load carrying ability of the structure. Since, at the end of the post – buckling, the body cannot carry load and crippling failure takes place. In this review article, crippling behavior of the composite structures is investigated. After describing the crippling phenomenon, this study mainly investigates both experimental and theoretical points of views. In this scope, affecting parameters such as stacking sequence, geometrical properties and boundary conditions are determined. Then, the improved theoretical approaches are stated. The compatibilities of the test results are assessed with theoretical studies. [ABSTRACT FROM AUTHOR]

• Buckling strength of metamaterial is designed by deep learning and improved compared with benchmark models, validated by 3D printing and compression testing. • The optimization proceeds to transition in dominant buckling mode from in-plane to out-of-plane deformation, converging the eigenvalue of 2nd mode to 1st mode. • The mechanism of superior buckling strength shows that thickness of horizontal beam does not significantly affect buckling strength and post-buckling behavior. Metamaterials are specially engineered materials distinguished by their unique properties not typically seen in naturally occurring materials. However, the challenge lies in achieving lightweight yet mechanically rigid architectures, as these properties are sometimes conflicting. For example, buckling strength is a critical property that needs to be enhanced since buckling can cause catastrophic failure of the lightweight metamaterials. In this study, we introduce a generative machine learning based approach to determine the superior geometries of metamaterials to maximize their buckling strength without compromising their elastic modulus. Our results, driven by machine learning based design, remarkably enhanced buckling strength (over 90 %) compared to conventional metamaterial designs. The simulation results are validated by a series of experimental testing and the mechanism of the high buckling strength is elucidated by correlating stress field with the metamaterial geometry. Our results provide insights into the interplay between shape and buckling strength, unveiling promising avenues for designing efficient metamaterials in future applications. [ABSTRACT FROM AUTHOR]

Tape-springs – straight strips with transversely curved cross-sections – undergo a flattening of the cross-section upon bending, and accompanying torsional buckling in equal-sense bending which then "recedes" at greater deformation. The exact analytical solution for tape-spring bending was solved by Mansfield; however, the resulting expression for the twisting curvature at the onset and recession of torsional buckling cannot be solved in closed-form. Approximate closed-form expressions are therefore sought: firstly, by utilising Taylor series approximations of Mansfield's extensive functions; and secondly, by assuming a uniform transverse curvature, thereby rendering the problem algebraic in nature, and deriving new governing expressions. Further approximations assume the cross-section does not deform upon bending, and that the tape-spring remains a developable surface in the inextensible limit of zero thickness. All approximate solutions are shown to agree closely with Mansfield's solution at small curvatures, with the uniform curvature approximation also capturing the recession of torsional buckling to a reasonable degree of accuracy. The accuracy of the uniform curvature approximation is related to a pertinent dimensionless parameter, which governs the size of a boundary layer in Mansfield's exact solution: as this parameter tends to infinity, the uniform curvature approximation and Mansfield's exact solution are shown to converge; as it tends to zero, all solutions are shown to converge on the inextensible limit. • Approximate solutions for tape-spring bending assuming uniform curvature. • Closed form expressions for the onset and recession of torsional buckling. • Approximate solution in good agreement with exact Mansfield solution. • Exact and approximate solutions converge in the zero-thickness inextensible limit. [ABSTRACT FROM AUTHOR]

This research aims to establish the semi-analytical approach for nonlinear dynamic buckling and vibration responses of functionally graded graphene platelet reinforced composite (FG-GPLRC) circular plates and spherical shells subjected to time-dependent radial pressure and thermal loads. The higher-order shear deformation theory with von Karman’s nonlinearities and the nonlinear viscoelastic foundation model is used to establish the expression of the fundamental equations of considered structures. The shells and plates are considered with clamped and immovable edge, and shallow curvature of the shells is applied. The Lagrange function is applied to establish the total energy of structures, and the potential function of viscous damping of the viscoelastic foundation is expressed using the Rayleigh dissipation function. The motion equation of the structures can be formulated using the Euler–Lagrange function. The dynamic responses are obtained using the numerical method, and the critical dynamic buckling loads are obtained using the dynamic buckling criterion of Budiansky–Roth. The large effects of material parameters, geometrical parameters, and nonlinear viscoelastic foundation on dynamic responses of considered structures are investigated and discussed in many numerical examples. [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]

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The contradiction of high subducting plate rate (ranging from 4 to 9 cm/yr on Earth's surface) and low slab sinking rate (about 1 and 2 cm/yr in lower mantle) calls for significant slab deformation in the middle mantle. However, mechanisms that can account for both the deformation and the rate discrepancy have not been fully explored. Here, using 2‐D numerical models that incorporate grain size evolution, we propose a new slab deformation mode, slab segmentation and stacking, to accommodate the differential slab sinking rates. Our results show that the segmented slab due to faulting and grain‐size reduction may further break off and stack over itself as it encounters the high‐viscosity lower mantle. Stacked slabs slowly sink in the lower mantle, while periodic slab tearing hinders upward stress transmission, allowing shallow plates to subduct at a higher rate. This discovered mode also provides an alternative explanation for slab thickening in the lower mantle. Plain Language Summary: According to observations and analysis, the velocities of plates entering the trench are much higher than the slab sinking rate in the lower mantle. Inconsistent velocities at the slab's two ends must be accommodated by slab deformation or accumulation in the middle mantle to ensure mass conservation. We have considered three different deformation modes: slab buckling, horizontal deflection, segmentation and stacking. Compared to the diffusive plastic weakening in the mode of slab buckling, previous studies have shown that slab faulting and grain size evolution can induce stronger localized weakening within slabs. Our study goes a step further by finding that the segmented slab can break off and stack over itself periodically when it encounters the lower mantle. This allows the slab to deform more easily in the mantle transition zone, enabling the plate to subduct at a higher rate while keeping the lower‐mantle slab sinks at a low rate. We also find that this mode of slab deformation can equally well explain the thickening of the slab in the lower mantle. Key Points: The discrepancy between the subducting plate rate and lower mantle slab sinking rate calls for slab accumulations in the middle mantleSimple buckling explains the accumulation but is not sufficient to accommodate the rate discrepancyThe mode of slab segmenting, breaking off, and stacking is a possible solution to the slab accumulation and rate discrepancy [ABSTRACT FROM AUTHOR]

During the operation of the drill string, it displays a degree of flexibility. Simultaneously, its dynamic properties, influenced by complex stress conditions, manifest nonlinearity and uncertainty. A comprehensive investigation into the dynamics of flexible drill strings is imperative for deep well drilling. This paper presents a model that simulates random interactions between a flexible drill string and the borehole wall, simplifying the actual drill string model using analogous principles. Dynamic simulation software is utilized for analysis, and an indoor experimental setup has been established. The results reveal that with a constant weight on bit (WOB), higher drill string rotational speeds correlate with increased susceptibility to buckling deformation. Additionally, the critical time for deformation onset exhibits a nearly linear relationship with rotational speed. Maintaining a constant rotational speed, an increase in WOB enhances the likelihood of buckling deformation. The experimental findings suggest a correlation between the drill string's rotation frequency and the WOB. [ABSTRACT FROM AUTHOR]

Hollow yttrium-stabilized zirconia (YSZ) particles, which are often used to prepare high porosity coatings in industry, hit substrate at a fully molten state or semi-molten state due to the high temperature gradient of particles caused by the low thermal conductivity. Considering the hollow solid core large deformation and liquid solidification during the deposition of semi-molten hollow particles (SMHPs), a fluid-structure interaction model described by the coupled Eulerian and Lagrangian (CEL) method, is developed and validated to investigate the spreading results in thermal spraying. The empirical formula of dynamic viscosity based on the ABAQUS CEL method is proposed and verified for simulation of the liquid YSZ spreading and solidification. The compression ratio and plastic dissipation are calculated to reveal flattening and buckling phenomena of hollow solid core with different initial velocities and hollow radius. Moreover, a double-SMHP impact model is established to simulate the interaction of particle-particle-substrate, and the effect of flattening, buckling and structural self-contact on porosity is analyzed. Numerical simulation results show that hollow solid core large deformation induces instability accompanied by flattening, buckling or structural self-contact, which results in the reduction of layer porosity. [ABSTRACT FROM AUTHOR]

We conducted an isogeometric analysis (IGA) to evaluate the performance of automobile structural member deformation and crash. In automobile crash analysis, ensuring the accuracy of the acceleration, velocity, and load in time series, as well as the structural deformation behavior, is important. To maintain the aforementioned consistency, accurately reproducing the bending and buckling of structural members is indispensable. In this study, we firstly computed the bending and buckling of structural members using IGA and validated its performance by comparing the results with those of a conventional finite element analysis and experiments. In addition, we utilized IGA for the crash analysis of an automobile body. [ABSTRACT FROM AUTHOR]

Wrinkling is a typical failure mode of sandwich structures with thin skins, where the bending deformation of face skins occurs simultaneously in conjunction with transverse stretching deformation of core layer. To analyze the three-dimensional (3D) deformation of wrinkling, a model is required to possess a capability describing completely different deformations at each ply. Therefore, by utilizing the Chebyshev polynomial at each layer of sandwich panels, this paper focuses on proposing a higher-order model to individually illustrate deformations of the skins and the core. By means of the proposed model, a refined triangular element has been constructed. By analyzing the stability of a sandwich plate without stiffeners, the finite-element formulation has been verified by comparing it to the quasi-3D elasticity solutions. In addition, it is anticipated that wrinkling failure can be effectively restrained by designing the stiffener layout. To this end, the influence of stiffener layouts on wrinkling behaviors of sandwich plates has been investigated in detail, and it is found that the capability of resisting the wrinkling deformation can be obviously improved by designing reasonable stiffener layouts. Moreover, the translation between buckling and wrinkling behaviors of sandwich panels with different stiffeners has been also explored, which can help to better understand wrinkling deformation mechanism. In summary, the proposed model can be used to design a reasonable arrangement of stiffeners to resist the wrinkling failure of sandwich panels. [ABSTRACT FROM AUTHOR]

Significant inelastic deformations induced in structural systems lead to structures possibly possessing some degree of permanent lateral deformation following major seismic events. These permanent deformations have led to considerable research being conducted over the past 20 years into developing structural systems that exhibit self-centring behaviour. For a structural system such as the concentrically braced frame (CBF), for which the dissipating mechanism is the tensile yielding and compressive buckling of the diagonal steel tubular members, these residual deformations present a problem when considering the structure's overall resilience to the seismic loading both during and after an event. This paper describes the numerical modelling of a novel self-centring, concentrically braced frame (SC-CBF) system that combines a conventional CBF with a self-centring arrangement to produce a structure that possesses the desirable lateral load-resisting capacity of the CBF but which also re-centres when subjected to many cycles of large inelastic brace deformation. First, an experimental test programme for the SC-CBF is briefly described, followed by a numerical model to capture the SC-CBF's characteristics during cyclic loading. This numerical model is validated using the experimental test data, showing that the experimental and numerical simulation data match rather well. This development presents a platform upon which further research through experimental testing and numerical simulation can be conducted. The proposed SC-CBF system can then be developed into a viable lateral load-resisting system that will provide a more resilient system than the current conventional CBF. [ABSTRACT FROM AUTHOR]

The traditional nonlinear aerostatic instability of long-span bridges is based on a two-layer iteration method that accurately predicts the structural equilibrium path before the critical buckling point. Due to strong nonlinearity after buckling, this traditional method cannot easily calculate the structural equilibrium and possible bifurcation using either Newton–Raphson or arc-length methods. In this study, a reduced order modeling (ROM) method for long-span bridge aerostatic deformation is proposed to approximate the bridge aerostatic equilibrium path after the critical point. The structural deformation mode shapes are extracted through singular value decomposition performed on the deformation matrix, and the nonlinear structural stiffness matrix is determined through the indirect displacement-based method on the finite-element method (FEM) platform. The ROM method is validated through comparison against the aerostatic deformation by the traditional two-layer iteration method based on FEM. By extending to higher wind speed, the ROM method can approximate the bridge deformation after initial buckling, and pitchfork bifurcation is observed after the structure undergoes rapid deformation growth. The stability of the equilibrium paths is examined through the Jacobian of restoring force vector, and the "snap-through" phenomenon exists for the equilibrium path before the bifurcation point. [ABSTRACT FROM AUTHOR]

To investigate the mechanical deformation characteristics of the 'Segment-SCC-Steel Tube' combined bearing lining structure under internal and external pressure, the loading device and monitoring system for the stability analysis of the full-scale lining were proposed. The effect of cracked encased concrete and local external pressure on the instability mode of thin-walled steel pipes was explored by full-scale model experiment and three-dimensional FEM numerical simulation. The influence of SCC (Self-Compacting Concrete) and stiffening rings on the stability of steel pipes subjected to external pressure was discussed. The results show that SCC cracks occur and intensify with increasing internal pressure. The external water acts directly on the steel tube through cracking, resulting in wavy deformation, and the gap between the SCC and steel tube further increases. When calculating the critical external pressure for the steel pipe, the constraint of encased concrete can be ignored, and only the constraint effect of the stiffening ring can be considered. Therefore, the Von Mises formula was used to predict the critical external pressure between the stiffening rings with high accuracy. In addition, the stiffening ring can mitigate the crack propagation of nearby SCC. The steel tube remained in the elastic stage under internal pressure. In the full-scale experiment, the external pressure could not continue to rise after reaching 0.65 MPa. Nevertheless, the amplitude of the buckling wave continued to increase. It is considered that the steel pipe is in an unstable state, and the failure mode is dominated by single-lobe buckling. • According to the performance of the 'Segment-SCC-Steel Tube' lining structure, the influence of cracked encased concrete and local external pressure on the buckling mode of steel pipes is investigated. • The loading device of the full-scale model test is proposed for the external pressure stability analysis of the 'Segment-SCC-Steel Tube' lining structure, and the monitoring system combining distributed optical fiber and traditional vibrating wire sensors is established. • The mechanical deformation characteristics of the SCC and Steel Tube lining under internal and external pressure are revealed, and the influence of SCC and stiffening rings on the stability of steel pipes under external pressure is discussed. [ABSTRACT FROM AUTHOR]

To study the effect of Grade 700 MPa longitudinal rebars and hoops on the deformation capacity of RC and composite columns, eight rectangular columns were tested under cyclic lateral loading and uniform axial compression. The test parameters were the hoop type (rectangular or spiral hoops), hoop spacing, the use of composite steel section, and the shape of cross section (square column or rectangular wall-column section). All columns exhibited ductile behavior after flexural yielding. Compared to rectangular hoops and crossties, spiral hoops significantly enhanced the deformation capacity of RC and composite columns by providing lateral confinement and by restraining local buckling and tensile fractures of longitudinal rebars. On the other hand, the use of embedded steel section had limited effect on the deformation capacity because of the relatively low yield strength of the steel section. In the case of wall-column section, as the section depth increased, the deformation capacity decreased due to the increased shear demand. Existing nonlinear analysis modeling methods were applied to the test specimens. The prediction results underestimated the tested deformation capacity, particularly for columns with spiral hoops. [ABSTRACT FROM AUTHOR]

Flexible lightweight arched structures are finding increasing use as components in smart engineering applications. Such structures are prone to various types of instability under moving transverse loads. Here, we study deformation and vibration of a hinged circular arch under a uniformly moving point load using geometrically-exact rod theory to allow for large pre- and post-buckling deformations. We first consider the quasi-statics problem, without inertia. We find that for arches with relatively large opening angle (∼ 160 ∘ ) a sufficiently large traversing load will induce an out-of-plane flopping instability, instead of the in-plane collapse (snap-through) that dominates failure of arches with smaller opening angle. In a subsequent dynamics study, with full account of inertia, we then explore the effect of the speed of the load on this lateral buckling. We find speed to have a delaying (or even suppressing) effect on the onset of three-dimensional bending–torsional vibrations and instability. Based on numerical computations we propose a power law describing this effect. Our results highlight the role of inertia in the onset of elastic instability. [ABSTRACT FROM AUTHOR]

Mechanical metamaterials are highly versatile structures capable of achieving unconventional mechanical properties. Of particular interest are mechanical metamaterials with the ability to tune bandgaps, offering potential applications in vibration control tailored to specific requirements. In this study, a new type of metamaterial is introduced to exhibit a distinctive two-step deformation mode under compressive displacement. Through a combination of numerical simulation and experimental verification, the band structure and vibration characteristics of the novel metamaterial in different stable states are thoroughly examined under compressive displacement. The results demonstrate that, in comparison to the initial structure, the novel mechanical metamaterial effectively addresses the issue of a significant reduction in plateau stress relative to buckling stress following buckling in the second deformation stage. The novel structure showcases notable controllable deformation capabilities, yielding distinct band structures in various stable states, and facilitating bandgap tuning. Furthermore, the study explores the influence of geometrical parameters and stable state transitions on bandgap evolution, supported by frequency response analyses and experimental validation. This research offers a fresh perspective on the utilization of Multistable Multi-Step Deformation Metamaterial (MMDM) for energy absorption and vibration damping applications. [ABSTRACT FROM AUTHOR]

There is limited research on the interaction mechanism between the buckling load of the side pile top and the soil pressure behind pile (SPP) with the side pile. As the side pile serves as a crucial component of the lining structure in the metro, using the pile-beam-arch (PBA) method, it plays a vital role in maintaining the mechanical stability and deformation control of the station's lining system. Based on the Guangzhou Metro Line 11 project, this paper delves into the impact of mechanical characteristics and deformation of the side pile using the PBA method. It considers various factors such as different buckling loads, including horizontal load of arch (HLA), vertical load of arch (VLA) and SPP and offers corresponding construction suggestions. Our findings indicate that the lateral displacement and deformation of the side pile are primarily influenced by the HLA. The optimal HLA value stands at 1200kN. As the HLA increases, the side pile undergoes a transformation from a forward-inclined deformation mode to a belly distension deformation mode when moving towards the station's interior. The influence of HLA on bending moments about the side pile surpasses that of axial force. The VLA exerts a more significant effect on vertical settlement of the side pile, yet its impact on lateral pile body deformation is minimal. An increase in HLA significantly impacts the axial force of the side pile, but has minimal effects on bending moments. The SPP holds significant influence on the stability of the side pile; hence, it is recommended to implement appropriate lining measures to guarantee stability when dealing with exceptionally high SPP values. [ABSTRACT FROM AUTHOR]

Multi-segment shell typical of underwater vehicles is currently important underwater equipment. Stealth performance is a key indicator to improve the working capacity of underwater vehicles. Low-noise design is an important means to improve stealthy performance. Accurate and effective identification of its structure Frequency Response Function (FRF) is the premise of low-noise design. However, the multi-section shell joint interface has many connection points, complex transmission path and typical nonlinear characteristics, which challenges the acquisition of its structural FRF. The Receptance Coupling Substructure Analysis (RCSA) is used to segment the multi-stage shell, which can realize the integration of finite element method and experimental method, and provide an effective way to obtain the FRF of multi-segment shell. At the same time, the multi-segment shell is a typical thin-wall structure, and its actual buckling process under impact is a nonlinear (large deformation) process. Therefore, the nonlinear joint interface is constructed based on linear connection, and the RCSA for nonlinear joint interface is studied. On the basis of accurately obtaining the FRF, it is of theoretical and application significance to study the low noise design of shell. [ABSTRACT FROM AUTHOR]

This study presents a modular, electronics‐free, and fully onboard control and actuation approach for shape memory alloy (SMA)‐based soft robots to achieve locomotion tasks. This approach exploits the nonlinear mechanics of compliant curved beams and carefully designed mechanical control circuits to create and synchronize rhythmic deformation cycles, mimicking the central pattern generators prevalent in animal locomotions. More specifically, the study elucidates a new strategy to amplify the actuation performance of the shape memory coil actuator by coupling it to a carefully designed, monostable curve beam with a snap‐through buckling behavior. Such SMA‐curved beam assembly is integrated with an entirely mechanical circuit featuring a slider mechanism. This circuit can automatically cut off and supply current to the SMA according to its deformation status, generating a self‐sustained rhythmic deformation cycle using a simple DC power supply. Finally, this study presents a new strategy to coordinate (synchronize) two rhythmic deformation cycles from two robotic modules to achieve efficient crawling locomotion but still use a single DC power. This work represents a significant step toward fully autonomous, electronics‐free SMA‐based locomotion robots with fully onboard actuation and control. [ABSTRACT FROM AUTHOR]

This paper utilizes a coupled chemomechanical model that integrates chemical reactions, diffusion, and mechanical deformation to describe the high-temperature interfacial reactions and stress evolution within an enamel coating/Ni-based super-alloy system. Through finite element simulation, we conduct a comprehensive analysis of multiple reactions and processes at the interface. Experimental characterization of the concentration distribution of various elements is employed to verify the accuracy of the proposed chemomechanical model. Additionally, the simulation reveals that the interface region experiences compressive circumferential stress, which can potentially lead to interfacial failure due to buckling. On the other hand, the enamel coating undergoes tensile circumferential stress, resulting in the formation of vertical surface cracks. These findings hold practical implications for the development of advanced coatings with enhanced durability and performance. Future research can further optimize coating design and enhance the reliability of high-temperature applications based on these results. [ABSTRACT FROM AUTHOR]

This study focuses on investigating how grid-stiffened composite shells behave under external hydrostatic pressure. The critical buckling load is calculated using the first-order shear deformation theory (FSDT) and the Ritz method. Various factors, including shell thickness, angle of helical stiffeners, rib section area, and the number of stiffeners, are examined to understand their impact on the buckling load. To optimize the design, three multi-objective optimization algorithms are employed: Nondominated Sorting Genetic Algorithm II (NSGAII), Multiobjective Particle Swarm Optimization (MOPSO), and a hybrid method that combines NSGAII and MOPSO. The hybrid method intelligently divides the population into two groups and uses NSGAII and MOPSO to efficiently explore and exploit the solution space. The results yield a Pareto optimal front that showcases diverse solutions across different regions, providing decision-makers with the flexibility to select the solution that best fits their preferences. The solutions obtained through these algorithms are compared based on their diversity and distribution throughout the Pareto front. [ABSTRACT FROM AUTHOR]

An innovative self-centering hybrid rocking braced steel frame (SCHRBF) with separate braced span and rocking span is proposed for improving seismic resilience. The braced span utilizes buckling-restrained braces (BRBs) to provide energy-dissipating capacity, and the rocking span consists of stiff rocking cores and self-centering braces (SCBs) to achieve a uniform inter-story drift distribution and low post-earthquake residual displacement under a strong earthquake. This study first describes the basic composition and nonlinear mechanical behavior of this novel system. Then, a force-based seismic design procedure for the SCHRBF system is proposed, including the determination and allocation of base shear, design of BRBs in braced span, design of SCBs in rocking span, and design of rocking core members. The influence of key design parameters on the seismic responses of the system is then explored through parametric analysis. And recommended values of the design parameters are provided according to the analysis results. Although the properly designed structure has significant partial re-centering behavior, its peak inter-story drifts, residual inter-story drifts, and deformation patterns can be effectively controlled under strong earthquakes. Finally, the superiority of the SCHRBF in controlling seismic displacement responses is verified by comparing with other structural systems. [ABSTRACT FROM AUTHOR]

The aim of this work is the derivation and examination of a material model, accounting for large elastic deformations, coupled with species diffusion and thermal effects. This chemo-thermo-mechanical material model shows three key aspects regarding its numerical formulation. Firstly, a multiplicative split of the deformation gradient into a mechanical, a swelling and a thermal part. Secondly, temperature-scaled gradients for a numerical design comprising symmetric tangents and, thirdly, dissipation potentials for the modelling of dissipative effects. Additionally, the derived general material model is specialised to thermoresponsive hydrogels to study its predictive capabilities for a relevant example material class. An appropriate finite element formulation is established and its implementation discussed. Numerical examples are investigated, including phase transition and stability phenomena, to verify the ability of the derived chemo-thermo-mechanical material model to predict relevant physical effects properly. We compare our results to established models in the literature and discuss emerging deviations. [ABSTRACT FROM AUTHOR]

The eastern Iranian range, known as the Sistan suture zone in the past, has recently been identified as the Sistan orogen. This Paleogene orogeny is located between the Lut and Afghan microcontinents. The structural analysis shows that most of the thrusts dip towards the NW so that the Permo-Triassic sediments and Jurassic micro-diorites of the Lut Block overthrusted over the younger rocks. Structural studies show that the tectonic vergence was from the NW to the SE of the Sechengi area in the NW part of Sistan orogen. We recognized three deformation phases in eastern Iran. The first N-S deformation event (D1) resulted in the formation of tight E-W folds (F1) and associated cleavages (S1). The second E-W deformation event (D2), which occurred in the late Paleogene led to the bending of older structures, including the axial plane of the first-generation folds giving them a new northwest direction (F2). Additionally, the ramp of the first-phase thrusts (striking E-W) was reactivated, acquiring a new NNW orientation and exhibiting SSE tectonic vergence. The third deformation event (D3) resulted in the formation of NNE and WNW conjugate faults in eastern Iran. Such consecutive deformation events perpendicular to each other are inconsistent with the models of simple linear orogen presented for eastern Iran (i.e. rifting of eastern Iran continental crust and subsequence linear collision) and seem more consistent with the buckling orogeny (Orocline). [ABSTRACT FROM AUTHOR]

A dual-phase lattice structure composed of mixed units with hard and soft phase characteristics is proposed in this work. The proposed lattice structure has high specific energy absorption and high compressive strength. The load response and energy absorption characteristics under bending loads were studied through three-point bending tests and numerical analysis methods. The research results indicate that although the deformation modes of the given lattice structure are the same, the dual-phase design strategy significantly improves the bending performance of the lattice structure: the bending modulus is increased by 744.7%, and the specific energy absorption is increased by 243.5%. [ABSTRACT FROM AUTHOR]

Strain engineering, as a powerful strategy to tune the optical and electrical properties of two-dimensional (2D) materials by deforming their crystal lattice, has attracted significant interest in recent years. 2D materials can sustain ultra-high strains, even up to 10%, due to the lack of dangling bonds on their surface, making them ideal brittle solids. This remarkable mechanical resilience, together with a strong strain-tunable band structure, endows 2D materials with a broad optical and electrical response upon strain. However, strain engineering based on 2D materials is restricted by their nanoscale and strain quantification troubles. In this study, we have modified a homebuilt three-points bending apparatus to transform it into a four-points bending apparatus that allows for the application of both compressive and tensile strains on 2D materials. This approach allows for the efficient and reproducible construction of a strain system and minimizes the buckling effect caused by the van der Waals interaction by adamantane encapsulation strategy. Our results demonstrate the feasibility of introducing compressive strain on 2D materials and the potential for tuning their optical and physical properties through this approach. [ABSTRACT FROM AUTHOR]

The rapid development of additive manufacturing (AM) has facilitated the creation of bionic lightweight, energy-absorbing structures, enabling the implementation of more sophisticated internal structural designs. For protective structures, the utilization of artificially controlled deformation patterns can effectively reduce uncertainties arising from random structural damage and enhance deformation stability. This paper proposed a bionic corrugated lightweight honeycomb structure with controllable deformation. The force on the onset state of deformation of the overall structure was investigated, and the possibility of controlled deformation in the homogeneous structure was compared with that in the corrugated structure. The corrugated structures exhibited a second load-bearing capacity wave peak, with the load-bearing capacity reaching 60.7% to 117.29% of the first load-bearing peak. The damage morphology of the corrugated structure still maintained relative integrity. In terms of energy absorption capacity, the corrugated lightweight structure has a much stronger energy absorption capacity than the homogeneous structure due to the second peak of the load carrying capacity. The findings of this study suggested that the combination of geometric customization and longitudinal corrugation through additive manufacturing offers a promising approach for the development of high-performance energy-absorbing structures. [ABSTRACT FROM AUTHOR]

This paper presents a large deformation Kirchhoff–Love shell model hierarchically enhanced with through-the-thickness warping functions, arbitrarily chosen by the user. Two unknowns are introduced for each of them, representing its amplitudes in two directions tangent to the shell surface. NURBS are used to approximate reference surface displacement and warping amplitudes in the weak form. The transverse shear strains are linear functions of the warping parameters only and naturally free from locking. A patch-wise reduced integration avoids membrane locking and improves efficiency. Particular attention is paid to the modeling of composites made up of multiple stiff layers coupled with soft interlayers. The alternating layup with high stiffness ratios induces a significant sectional warping with transverse shear strains concentrated in the soft layers. Two warping models are investigated: (WI) all stiff layers maintain the same director orthogonal to the deformed surface with independent transverse shear deformations of the soft layers; (WZ) a single zigzag function linking these deformations. The numerical tests confirm the great accuracy of the hierarchic shell model in reproducing the solid solution with a small number of discrete parameters, provided that the correct warping model is chosen. WI is reliable for all alternating layups. WZ reduces the unknowns to five per surface point, regardless of the number of layers, and is accurate for uniform soft layers. • The Kirchhoff–Love composite shell is enhanced with warping. • The hierarchic approach is used for large deformations. • Transverse shear strains and zigzag effects are included. • An accurate and efficient isogeometric formulation is proposed. • Two warping models are studied for stiff/soft layups. [ABSTRACT FROM AUTHOR]

Frequency‐selective surfaces (FSS) with flexible treatment can be employed in various applications. This paper develops a mechanically constructed flexible double‐layer adjustable FSS based on a 3D cross‐shaped kirigami structure design. Through mechanical stretching, the kirigami structure partly adhered to the ecoflex substrate enables this FSS to modulate the resonant frequencies of two filter bands synchronously. Meanwhile, the structural deformation triggered by mechanical stretching may function as a switch to adjust the filter band with a higher resonant frequency. According to the results of EM experiments and simulations, in the absence of stretching, the undeformed FSS with a double‐layer structure has two filter bands. Compared to the undeformed configuration, the stretching induces structural deformation, which results in apparent resonant frequency shifts of both the two filter bands and the contraction of the filter band with higher resonant frequency. A buckling model that has been theoretically, cumulatively, and experimentally proven is utilized to investigate the structural deformation of this FSS caused by stretching. It is convenient to switch flexible double‐layer adjustable FSS' deformation by mechanical method. This flexible double‐layer adjustable FSS offers a new design strategy for the application of FSS, paving the route for new developments in electromagnetic compatibility. [ABSTRACT FROM AUTHOR]

A micromorphic computational homogenization framework has recently been developed to deal with materials showing long-range correlated interactions, i.e. displaying patterning modes. Typical examples of such materials are elastomeric mechanical metamaterials, in which patterning emerges from local buckling of the underlying microstructure. Because pattern transformations significantly influence the resulting effective behaviour, it is vital to distinguish them from the overall deformation. To this end, the following kinematic decomposition into three parts was introduced in the micromorphic scheme: (i) a smooth mean displacement field, corresponding to the slowly varying deformation at the macro-scale, (ii) a long-range correlated fluctuation field, related to the buckling pattern at the meso-scale, and (iii) the remaining uncorrelated local microfluctuation field at the micro-scale. The micromorphic framework has proven to be capable of predicting relevant mechanical behaviour, including size effects and spatial as well as temporal mixing of patterns in elastomeric metamaterials, making it a powerful tool to design metamaterials for engineering applications. The long-range correlated fluctuation fields need to be, however, provided a priori as input parameters. The main goal of this study is experimental identification of the decomposed kinematics in cellular metamaterials based on the three-part ansatz. To this end, a full-field micromorphic Integrated Digital Image Correlation (IDIC) technique has been developed. The methodology is formulated for finite-size cellular elastomeric metamaterial specimens deformed in (i) virtually generated images and (ii) experimental images attained during in-situ compression of specimens with millimetre sized microstructure using optical microscopy. The proposed IDIC method identifies the different kinematic fields, both before and after the microstructural buckling, and without any prior knowledge determines correctly the relevant patterning modes required by the homogenization scheme. It is further argued that patterning modes are independent of the unit cell size, the hole diameter to cell size ratio, as well as local material properties, allowing for modelling and design of (finite- and infinite-size) metamaterials and specimens with graded microstructures in terms of geometry and/or material properties. It is shown that the proposed methodology is also applicable to cellular metamaterials and structures with different microstructural designs. • Decomposition of cellular metamaterials kinematics by an ansatz from literature. • Development of a novel Micromorphic Integrated Digital Image Correlation scheme. • Unravelling long-range correlated fluctuation modes & their spatial distributions. • Identification of micromorphic fields achieved directly from in-situ test images. [ABSTRACT FROM AUTHOR]

Edge-on atomic layers in layered solids undergo buckling, which creates a structure referred to as a "ripplocation." A collective set of multiple ripplocations is referred to as a "ripplocation boundary." In this study, in order to investigate the impact of lattice defects on ripplocation, we investigate the buckling deformation of graphene with lattice defects under confinement. To this end, we conducted confined uniaxial compression simulations by placing graphene sheets with various lattice defects between silicon atomic layers. Different types of lattice defects affect the mechanical properties of graphene, the results show that Young's modulus of graphene with the (1,0)_5 dislocation pair was the maximum at 494.6 GPa, whereas the Young's modulus of the (1,2)_10 dislocation pair was the minimum at 309.5 GPa. In addition, we employed a differential geometry method to study the out-of-plane deformation of a single-layer graphene system. Further, we used the nudged elastic band method for various types of lattice defects in graphene to uncover the minimum transition pathways, activation energy required to move from the (1, 0) dislocation pair to the (1, 1) pair is 44.916 eV. In particular, the results indicate that graphene with lattice defects exhibit kink deformation after buckling compared to that of perfect graphene. Our study not only explores the deformation of ripplocations and kink boundaries in layered solids but also provides a more comprehensive description influencing lattice defects on the nucleation mechanism and mechanical changes of ripplocations in graphene. • Investigated the impact of inducing lattice defects into graphite on the deformation of ripplocation. • Employed the nudged elastic band method to calculate the minimum energy pathways for various lattice defects. • Utilized differential geometry methods to compute curvature, observing significant variations at lattice positions. [ABSTRACT FROM AUTHOR]

To realize the one‐dimensional deformation of morphing wings, zero Poisson's ratio (ZPR) honeycomb metamaterials have become a popular research topic due to their lightweight, low in‐plane modulus, and high out‐of‐plane strength. A ZPR honeycomb metamaterial is designed and prepared from short‐cut carbon fiber‐reinforced polyetheretherketone (CF/PEEK) by a 3D printer. The mechanical properties of ZPR honeycomb metamaterials were tested to determine their tensile and bending stiffness. The results show that the metamaterial can achieve 62.3% ± 3.3% in‐plane elastic deformation after optimized structure design. At the same time, metamaterial has a certain bending resistance to keep the airfoil from normal buckling deformation. Moreover, a new test method for evaluating the cycle deformation behavior of flexible morphing wings is proposed. The high‐speed cyclic tension‐compression test showed that H22‐t0.6‐CT has the best stability, which may be related to its lower porosity (2.15% ± 0.12%). These results indicate that ZPR honeycomb metamaterials have great application prospects in the field of morphing wings. Highlights: The printed CF/PEEK wire is treated as a transversely isotropic material.ZPR honeycomb metamaterial allows for more than 50% in‐plane deformation.A new test method to evaluate the cyclic deformation behavior. [ABSTRACT FROM AUTHOR]

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• Reverse engineering make possible analyzes that were previously too labor-intensive. • Limitations in the laser scanning method still exist, but are not critical. • The point cloud enables the analysis of a real, deformed structure. • Size of the structure and the lack of access to the elements are not limitations. • It is possible to determine the beam axis curvature and geometry buckling. Reverse engineering is a method of obtaining information about the geometry of an existing object. To obtain such information, among others: 3D laser scanning is used. The result of measurements using this method is a point cloud. The research examined the possibilities of using scanning data to analyze the technical condition of a historical building. Based on the inventoried point cloud, the deflections of beams and ceilings were determined. The course and width of scratches, cracks and defects were determined. It was found that the basic factor increasing the usefulness of the point cloud for various analyzes is its density, which depends on the accuracy of the scan performed. Thanks to a detailed point cloud, a digital three-dimensional model (digital twin) of the existing object was created and analyzed using computer methods. The aim of the presented research was to evaluate the use of reverse engineering to analyze the condition of a historic water tower. Moreover, the real possibilities and advantages of a relatively new measurement method were checked. The thesis was put forward that laser scanning and reverse engineering are effective methods supporting the assessment of the building condition. Based on the available literature and in situ tests, the problem was described and analyzes were carried out to assess the condition of the historic water tower building. Measurements with a 3D laser scanner and a tachymeter were also carried out in the field. Then, the digital model was used to measure the deflection and possible buckling of beams and ceilings on individual floors. The correctness of the formulated method for solving the problem was verified on the basis of tests of sample structural elements. It has been shown that it is possible to directly identify the elevations of the bottom of the ceiling elements and verify whether the existing deflections do not exceed the standard limits. As research has shown, a point cloud resulting from reverse engineering is helpful in assessing the technical condition of a building. Combining classic inspection-based methods with the capabilities of the new measurement method allows for more accurate and broader analyses. [ABSTRACT FROM AUTHOR]

Tension–compression asymmetry, thermal-mechanical coupling, and finite deformation effects are common characters of many biological materials and engineering structures. By introducing different elastic constants under tension and compression, a thermo-mechanical bi-modulus constitutive model and a subsequent efficient computational analysis framework are proposed in the finite deformation regime. After we validate the convergence, accuracy, and robustness of the algorithm, we investigate the mechanical behavior of human brain tissue under varying intracranial pressure and temperature. Furthermore, with the use of the proposed bi-modulus thermoelasticity model, the classic tension-field theory is regularized, and wrinkling region and its evolution in membranes under thermomechanical loads can be effectively predicted, as an alternative to the computationally intensive post-buckling analyses. • A constitutive law accounting for TCA, thermal-mechanical coupling, and finite deformation effects is proposed. • An efficient iterative method for bi-modulus thermoelastic structures is developed. • Thermoelastic responses of human brain tissue is simulated. • Wrinkling regions of membranes in thermo-mechanical environment are efficiently predicted. [ABSTRACT FROM AUTHOR]

We present a computational method capable of modeling 3D flow-induced deformation of thin, highly compliant, hyperelastic vessels conveying viscous, inertial fluid. The method can uniformly consider vessel extension and collapse. Very large inflation, transient deformation, complex flow features as well as highly complex buckling shapes are well resolved by this method. The methodology combines finite volume and spectral methods for fluid motion, finite element method for structural mechanics of the vessel wall, and the immersed boundary method for two-way coupling between the wall and fluid. A hybrid of the continuous forcing and the ghost node methodologies capitalizing on the strengths of each is developed. The method avoids the surface instability encountered with the continuous forcing methods, as well as the need for domain remeshing as required in the iterative and partitioned approaches. The vessel wall can follow linear or nonlinear (strain softening and hardening) material models, and the fluid inertia can vary over a wide range. We demonstrate the versatility of the method by considering vessel inflation and collapse with large, complex, and transient deformation. Remarkable differences in vessel inflation at low versus moderate inertia are observed; this includes steady versus oscillatory motion, emergence of flow recirculation and pressure wave reflection which are well resolved. For the collapsing vessels, well-defined shapes with different buckling modes as well as highly complex buckling with fine surface folds are predicted. Additionally, a second-order correction to the well-known law of Laplace is developed and used to validate our computational results for vessel inflation. • A method for large deformation (extension and collapse) of highly complaint, hyperelastic vessels. • A hybrid of the continuous forcing and the ghost node methodologies capitalizing on the strengths of each. • A bending energy-based approach for collapsing vessel that has not been considered before. • A 2nd order correction to the well-known law of Laplace developed and used to validate computational results. [ABSTRACT FROM AUTHOR]

Mechanical metamaterials exhibit remarkable design versatility, enabling a series of unconventional mechanical properties via structural modifications. However, it is worth noting that many existing mechanical metamaterials either possess a singular deformation path or only multi-step deformation paths without reusability. This study proposes a novel multi-step deformation metamaterial that possesses multiple stable configurations. This metamaterial produces a unique two-step deformation mode under displacement loading, where the curved beams of the unit cells undergo snap-through and the vertical beams buckling. The influence of geometrical parameters on the multistability of the structure is thoroughly examined, and a theoretical prediction model for the buckling load is formulated. To validate the accuracy of the model, experimental tests and finite element simulations are conducted on the two-step deformation mode of periodic array of the unit cell. Additionally, a bi-material design approach for the unit cell is further introduced to enhance the specific energy absorption of the structure while reinforce the negative stiffness effect. Leveraging the multistable characteristics of the structure, mechanical logic gates such as AND, OR, NOT and NAND are conceptualized and experimentally validated. Through the implementation of rational designs and combinatorial connections within the logic gate structure, more complex logic operations can be realized. [ABSTRACT FROM AUTHOR]

Elastic ribbons possess the capacity to undergo stretching, bending, and twisting, resulting in a diverse range of morphologies. In this study, we conduct both experimental and numerical investigations into the torsional instabilities of clamped ribbons subjected to stretching and twisting loads. The extended Föppl-von Kármán plate model is employed to describe the torsional and tensile responses prior to buckling. Through finite element simulations, we accurately capture the observed evolution of morphologies, spanning from the initial helicoid to a double-layer helicoid, and ultimately to a scrolled yarn structure. As the formation of the double-layer helicoid, the torque, which decreases with the twist during the transverse bending and folding process, gradually increases with the twist until the occurrence of a secondary instability. Furthermore, initial pre-tension enhances the ribbon's capacity to endure torsional deformation, leading to corresponding increases in torque and tension. These findings hold implications for comprehending the intricate deformation mechanisms of slender structures. • The experimental morphological transitions of a twisted ribbon, from helicoid to double-layer helicoid, and finally to a yarn configuration, are captured through FE simulation. • The formation of the double-layer helicoid in the ribbon enables it to withstand transverse bending once more until the occurrence of secondary instability. • Pre-tension enhances the ribbon's capacity to endure torsional deformation, resulting in corresponding increases in torque and tension. [ABSTRACT FROM AUTHOR]

• The deformation behaviors of aluminum honeycomb sandwich panels with artificial defects of different sizes under in-panel compression were investigated using mirror-assisted MV-DIC. • Dual-surface in-plane deformation fields and through-thickness strain fields were measured. • The honeycomb sandwich panel exhibits local undulations and strain concentrations in the surface with defects. • Only defects with sufficiently large sizes leads to decreases in the buckling load. • The bending direction of the buckled specimen is influenced by the local undulations caused by the defect. Honeycomb sandwich panels have been extensively utilized in the aerospace and automotive industries for their prominent advantages of energy absorption, high strength and tailorable anisotropic mechanical properties. Nevertheless, the common presence of local core-to-skin disbonding poses an urgent need to understand the mechanical behaviors of defective honeycomb sandwich panels. The present work investigates the deformation behaviors and evolutions of aluminum honeycomb sandwich panels with varying sizes of circular artificial core-to-skin disbonding defects using mirror-assisted multi-view digital image correlation (MV-DIC). Based on the 3D profiles and dual-surface deformation fields obtained with mirror-assisted MV-DIC, it is revealed that disbonding defects induced local surface undulations with severe local strain concentrations and determined the mode of gradual bending and buckling. Defects with a diameter below 20 mm induced minor local surface undulations and slight decreases in buckling load. When the diameters of defects reach 30 mm, extensive surface convex deformation occurs and the buckling load decreases by 23 %. The results validate mirror-assisted MV-DIC as a cost-effective and practical technique for characterizing dual-surface 3D deformation of sheet composite materials and structures. [ABSTRACT FROM AUTHOR]

• An induced energy absorption structure (IEAS) with altering load transfer paths is designed inspired by the growth and deformation of tree branches. • The asymmetric buckling mode of the proposed structure exhibits higher mechanical properties compared to symmetric linear buckling. • Through the gradient design of the structures, the asymmetric buckling mode is implemented in multi-layer IEAS. Negative stiffness (NS) structures with curved beams easily experience beam fracture in small-scale designs, limiting their repeatability and energy absorption. The induced energy absorption structure (IEAS), which achieves negative stiffness by altering load transfer paths, is designed inspired by the growth and deformation of tree branches. By means of the variation method of geometric parameters, a unique asymmetric buckling deformation mode is realized in IEAS. The NS and energy absorption characteristics in IEAS are analyzed based on load distribution and major principal strain theory. Compression results demonstrate that the asymmetric buckling mode exhibits higher energy absorption and specific energy absorption compared to symmetric linear buckling, effectively improving structural toughness. Through gradient analysis of geometric parameters and comprehensive analysis of induced structure layouts, the asymmetric buckling mode is successfully implemented in multi-layer IEAS. The multi-layer IESA exhibits excellent ability of energy absorption and toughness, making it have potential applications in areas that require small-sized designs with high energy absorption capabilities. [ABSTRACT FROM AUTHOR]