Bending Behavior Research Articles

Bending behavior of segmental precast diaphragm walls using bolted sleeve joints

AbstractTo study the bending behavior of segmental precast diaphragm walls using bolted sleeve joints, 2 full size specimens were tested. Both BC and EC specimens were connected using bolts with steel sleeves as positioner. BC specimen was consisted of two fully RC plates while EC specimen had precast holes in the concrete walls for lightweight treatment. Ultimate strengths, deformations, strains and failure modes were obtained from the test results. Finite element models were developed using ABAQUS and verified against the test results. The verified finite element models were used to further analyze the stress state of specimens under different loading. It indicated that the bolted sleeve joint exhibited good bearing capacity and bending stiffness. The lightweight treatment in the concrete part had minor effect and the design requirement could be satisfied.

A Comparison of Pneumatic Actuators for Soft Growing Vine Robots.

Soft pneumatic actuators are used to steer soft growing "vine" robots while being flexible enough to undergo the tip eversion required for growth. In this study, we compared the performance of three types of pneumatic actuators in terms of their ability to perform eversion, quasi-static bending, dynamic motion, and force output: the pouch motor, the cylindrical pneumatic artificial muscle (cPAM), and the fabric pneumatic artificial muscle (fPAM). The pouch motor is advantageous for prototyping owing to its simple manufacturing process. The cPAM exhibits superior bending behavior and produces the highest forces, whereas the fPAM actuates fastest and everts at the lowest pressure. We evaluated a range of dimensions for each actuator type. Larger actuators can produce more significant deformations and forces, but smaller actuators inflate faster and can evert at a lower pressure. Because vine robots are lightweight, the effect of gravity on the functionality of different actuators is minimal. We developed a new analytical model that predicts the pressure-to-bending behavior of vine robot actuators. Using the actuator results, we designed and demonstrated a 4.8 m long vine robot equipped with highly maneuverable 60 × 60 mm cPAMs in a three-dimensional obstacle course. The vine robot was able to move around sharp turns, travel through a passage smaller than its diameter, and lift itself against gravity.

Predicting plastic behavior of magnesium alloy tube bending with comprehensive constitutive models

This paper aims to predict defects occurring in magnesium alloy tube bending through finite element simulations. Deformation tests were conducted to identify and characterize plastic anisotropy, tension-compression asymmetry, and anisotropic hardening behaviors of extruded Mg–Al–Zn-RE alloy rectangular tubes. Limited by size, the deformation tests along the wall thickness of specimens were conducted through crystal plasticity analysis. To thoroughly investigate the material constitutive features affecting bending, two constitutive models, Yoon2014 and Hill48, were established and calibrated. The non-associative flow rule was adopted, and anisotropic hardening was depicted using the yield-surface interpolation method. In comparison, the Yoon2014 model accurately predicted the strain distribution and tube shape collapse of the bent tube with negligible deviation from the experimental data, prior to the Hill48 model. This underscores the necessity of considering comprehensive plasticity models in tube bending simulations.

Numerical and experimental studies on bending behavior of circular aluminium-concrete-steel double skin tubular cross-sections and bending capacity design approach

Considering the excellent corrosion resistance of aluminium alloy, a new-type aluminium-concrete-steel double skin tubular (ACSDST) member is proposed by replacing the outer steel tube of concrete-filled double skin steel tubular members with an aluminium alloy tube to improve structures' corrosion resistance and durability. Until now, no literature has been available on ACSDST cross-section in bending. This paper presents experimental and numerical investigations on the flexural behaviour of circular ACSDST cross-sections in bending. Broad parameters are examined in this research, including varying diameter-to-thickness ratios of the outer tube (20–120), hollow ratio (0.2–0.75), concrete compressive strength (30–70 MPa) and steel yield strength (235–355 MPa). The experimental results show that the final failure is controlled by the tensile rupture of aluminium alloy tubes, but it generally happens after the maximum moment, and the composite section behaves in good curvature ductility. The parametric analysis based on the developed finite element (FE) model discloses the different influences of diameter-to-thickness ratios of the outer tube, hollow ratio, and concrete and steel strengths on the bending moment capacity. Among them, the diameter-to-thickness ratio of the outer tube and hollow ratio significantly affect the bending moment capacity. The design equations for bending moment capacity are induced based on the plastic stress distribution method. Those equations are safe and accurate for the maximum moment (a widely used definition of bending moment capacity) within a certain range of parameters. However, a reduction factor 0.9 is proposed for the equations to predict the moment at a longitudinal flexural tensile strain of 1% (another widely used definition of bending moment capacity). Moreover, the cross-section slenderness limit for the compact ACSDST section is recommended based on the analysis of the experimental and FE results.

Free vibration analysis of tall buildings using a generalized continuous model: simplified approach to soil-structure interaction

Currently, due to the simplifications imposed on continuous models, there is an absence of a generalized approximate solution to investigate all possible dynamic behaviors of a tall building. In an attempt to address this deficiency, this paper proposes a new generalized continuous model and its solution methods to generalize all types of behavior that may be encountered in structural systems and tall buildings. The continuous model results from a composite beam that serially couples the classical sandwich beam and a pure shear beam. Unlike existing continuous models, the serial coupling, inclusion of new kinematic fields, and inclusion of rotational inertia allow for the resolution of complex interaction among different types of bending and shear behaviors. Specifically, it is shown how local shear behavior simultaneously interacts with global bending behavior, global shear, and local bending. Two solutions to the dynamic problem are presented: a closed-form analytical solution method for structures with uniformity along their height, and a numerical method that combines the advantages of the continuous method and the transfer matrix method to resolve structural and geometric variability in height. The transfer matrix is analytically solved by maintaining a fixed 6 × 6 matrix range that is independent of the number of levels of the structure, drastically reducing computational cost by eliminating the classical need to calculate the inverse of the zero matrix. Numerical applications investigate the effect of rotational inertia and local shear on the accuracy of the proposed results compared to results from the finite element method. To this end, a parametric analysis of 1560 different cases covering a wide range of typical behaviors in individual structural systems and tall buildings is conducted. The results exhibit promising accuracy, showing that the qualities of the proposed continuous model significantly improve precision compared to classical continuous models and therefore justify its practical application by academics and practicing engineers. Furthermore, the proposed mathematical approach is easily applicable in various domains of composite materials engineering.

Analyses of wrinkling mechanisms during forming of multi-layer woven fabric reinforced thermoplastic prepregs

Thermoplastic composites have made their way into the aerospace industry. The forming of prepregs with different ply orientations induces both intra-plane shear and inter-ply slippage behaviors, and the wrinkling risk is strongly increased by improper parameter control. This paper aims to investigate the deformation behavior of prepreg with different ply orientations and of wrinkling mechanisms during forming. A simulation approach of multi-layer thermoplastic prepreg based on a variable friction model with Stribeck curves and a non-orthogonal constitutive model is developed. The relationship between the local fiber deformation and the development of wrinkle defects is revealed. The results show that the balance between the three deformation mechanisms of shear, bending, and slippage behaviors determines the preform quality. Fiber compression induced by inter-ply friction is the main mechanism of wrinkle defects in the forming process of multi-layer thermoplastic prepregs.

Bending behavior and design of tapered lightweight CFDSST with large hollow ratio

Given the tremendous potential of tapered lightweight concrete-filled double-skin stiffened steel tubular members with large hollow ratio in engineering structures, such as building structures and wind turbine tower, the bending behavior of these members, distinguished by their large hollow ratio, lightweight concrete fill, and longitudinal stiffeners, was the focus of this study. Eleven specimens were tested under four-point bending loading. The failure modes, deflection curve distributions, moment-deflection curves, and strain development of specimens were discussed. The results indicate that the maximum deformation of the specimens is located near the smaller section in the constant moment region. Cracking was observed in the tension side concrete, and the outer edge of the compression side concrete was crushed. The validated finite element model was used for mechanical analysis and parametric study, where the stress development process in the member and the influence of parameters such as hollow ratio, steel tube diameter-to-thickness ratio, material strength, and tapered angle on the bending strength of the member were explained and discussed. Based on the results of experimental and numerical analyses, a novel method for predicting the bending strength was proposed. This method was shown to accurately predict the bending strength of concrete-filled double-skin steel tubular members.

A semi-analytical simulation method for bi-directional functionally graded cantilever beams under arbitrary static loads

This paper presents a novel semi-analytical simulation approach for analysing the behaviour of bi-directional functionally graded cantilever beams subjected to arbitrary static loads, such as concentrated moments, concentrated forces, distributed force and their combinations applied at any location along the beam. The fundamental equations governing the cantilever beam’s response are derived, on the basis of which the proposed semi-analytical method is implemented using MATLAB programming language. The simulation results include field variables as well as stress contours, providing a compressive understanding of the beam’s behaviour. To validate the accuracy and reliability of the proposed method, a convergence study is conducted in comparison with the graded finite element method (GFEM) and analytical solutions. In the end, the developed method is applied to simulate the bending behaviour of bi-directional functionally graded cantilever beams under various loads individually and their combinations. The stress contours and deflection curves obtained from the simulation are compared with the solutions obtained using GFEM, revealing that the developed method possesses excellent capability in accurately simulating the bending behaviour of cantilever beams.

Concave and convex small radius bending behavior of single and multiple layers reinforcement fabrics

Multilayer reinforcement fabrics are increasingly used for manufacturing structural polymer composites. In liquid molding processes, dry reinforcement fabrics are draped on a mold first, and infused with a liquid resin such as an epoxy in a subsequent manufacturing step. This presents major advantages in terms of operational flexibility and costs. However, draping multilayer reinforcement fabrics on complex mold geometries is challenging. Small radius mold corners constitute a major manufacturing challenge as they lead to variability in dry fabric positioning and resin-rich corners in polymer composite parts. Spring-back of fabrics bent over or into single curvature mold corners is a widespread industrial concern. However, contrary to draping over double-curvature surfaces, bending spring-back from convex or concave single-curvature corners has received very limited attention. No testing method is available. This paper quantifies reinforcement fabric bending spring-back. Single and multiple layer stacks were bent along three directions over convex and into concave 90° corners with five radii spanning 1.59 mm to 12.70 mm. In all cases, five replicated tests enabled variability quantification. Fabric stacks were also quantified using cantilevered bending tests for comparison purposes. Mold radius was found to affect the behavior to a larger extent than testing direction, number of layers or use of a binder.

Nonlinear bending behavior of functionally graded porous beams based on sinusoidal shear deformation theory

Nonlinear bending behavior of functionally graded porous beams based on sinusoidal shear deformation theory

Investigating mechanical properties and bending behavior of an auxetic plate with 4-star unit cell

This study derives the constitutive relationships between stress resultants and strain measures for 4-star auxetic structures using force-moment analysis of a representative unit cell and the Castigliano strain energy method. To validate the accuracy of the constitutive model, bending analysis is performed for a 4-star auxetic rectangular plate under Levy boundary conditions. The analytical and numerical results show excellent agreement, confirming the validity of the constitutive relations extracted from the generic 4-star unit cell. This work establishes a theoretical framework for designing 4-star auxetic metamaterials and demonstrates their potential for diverse engineering applications.

Transient bending analysis of the graphene nanoplatelets reinforced sandwich concrete building structure validated by machine learning algorithm

This paper demonstrates a thorough examination of the bending behavior of sandwich concrete building structures that are reinforced with graphene nanoplatelets (GPLs). The analysis is confirmed using a machine learning technique. Sandwich structures have notable benefits in terms of strength, longevity, and thermal insulation, making them well-suited for many building applications. Integrating GPLs into the concrete matrix improves the mechanical characteristics and performance of these structures, especially in terms of bending behavior. This study utilizes a machine learning technique to verify the characterization of the temporary bending behavior of a concrete building structure reinforced with graphene nanoplatelets. The approach utilizes a dataset consisting of simulated bending data to create a prediction model that can reliably estimate the temporary bending response of the reinforced structure under different loading situations. The machine learning algorithm’s effectiveness and dependability in optimizing the design and performance of graphene nanoplatelets reinforced sandwich concrete building structures are demonstrated through validation against simulated results. This provides engineers and designers with a powerful tool. This study enhances the comprehension and use of machine learning approaches in analyzing and designing sophisticated structural materials and systems.

Enhancing the Mechanical Performance of Concrete Slabs through the Incorporation of Nano-sized Iron Oxide Particles (Fe2O3)

The utilization of recycled iron in durable concrete production has gained attention for enhancing sustainability and resource efficiency. Simultaneously, incorporating nanoparticles as supplementary cementitious materials (SCMs) offers significant benefits. Introducing nano-sized iron particles (Fe2O3) into the cement paste results in a compact microstructure, improving strength, and durability. In this study, we investigate the bending behavior of concrete slabs reinforced with Fe2O3 nanoparticles using the non-local quasi-3D shear deformation theory based on Eringen's non-local differential constitutive relations. To characterize the elastic material properties of the nanocomposite, we employ Eshelby's homogenization model. In order to extend the applicability of our findings, we assume that the concrete plate rests on Kerr's foundation, which includes a shear layer connected to upper and lower springs. By deriving the equations of motion using the principle of virtual work, we establish a comprehensive framework for analyzing the bending of the concrete plate. To solve the equilibrium equations for a simply supported concrete plate, we present Navier's analytical solutions. Our investigation considers various influential parameters, such as the concentration of Fe2O3 nanoparticles in the concrete matrix, the elastic constants of the soil medium, different types of bending loads, and size-dependent nonlocal parameters. One of the most captivating findings of this study is that the incorporation of 30 wt% of iron nanoparticles in concrete leads to a remarkable improvement of 60% in the elastic properties of the material. Additionally, this same amount of iron nanoparticles has shown the potential to reduce the deflection of thin plates by over 60%.

Introducing ANN-GP algorithm to estimate transient bending of the functionally graded graphene origami-enabled auxetic metamaterial structures

This article presents a new method called the artificial neural networks-genetic programming (ANNs-GP) algorithm, which effectively predicts the bending behavior of functionally graded graphene origami-enabled auxetic metamaterial (FG-GORAM) structures under transient conditions. Functionally graded materials (FGMs) display spatial heterogeneity in their composition and microstructure, resulting in distinctive mechanical characteristics that make them well-suited for a wide range of engineering applications. The objective of this study is to create a prediction model that can accurately capture the intricate transient bending behavior of FGM structures. To do this, the researchers have used the ANN-GP technique, which combines ANNs with GP. The ANN component acquires knowledge from a dataset including actual or simulated bending data, while the GP component fine-tunes the structure and parameters of the neural network to improve its ability to make accurate predictions. The proposed algorithm combines the strengths of ANNs and GP to accurately predict the bending behavior of FG-GORAM structures. This algorithm is robust and efficient, allowing designers and engineers to optimize the performance and reliability of these structures in various applications. The effectiveness of the ANN-GP method is proved by comparing it to experimental or simulated data. This shows that the algorithm has the potential to be a useful tool for designing and analyzing sophisticated materials and structures.

Biobased Inks Based on Cuttlefish Ink and Cellulose Nanofibers for Biodegradable Patterned Soft Actuators.

Soft actuators with stimuli-responsive and reversible deformations have shown great promise in soft robotics. However, some challenges remain in existing actuators, such as the materials involved derived from nonrenewable resources, complex and nonscalable preparation methods, and incapability of complex and programmable deformation. Here, a biobased ink based on cuttlefish ink nanoparticles (CINPs) and cellulose nanofibers (CNFs) was developed, allowing for the preparation of biodegradable patterned actuators by direct ink writing technology. The hybrid CNF/CINP ink displays good rheological properties, allowing it to be accurately printed on a variety of flexible substrates. A bilayer actuator was developed by printing an ink layer on a biodegradable poly(lactic acid) film using extrusion-based 3D printing technology, which exhibits reversible and large bending behavior under the stimuli of humidity and light. Furthermore, programmable and reversible folding and coiling deformations in response to stimuli have been achieved by adjusting the ink patterns. This work offers a fast, scalable, and cost-effective strategy for the development of biodegradable patterned actuators with programmable shape-morphing.

Nonlinear bending characteristics of multidirectional functionally graded porous panels using higher-order finite element solution with parametric optimization

The current study aims to investigate the nonlinear bending behavior of unidirectional (1D) and multidirectional (2D/3D) functionally graded porous shell panels. Here, the material properties of the multidirectional functionally graded (FG)-panels are estimated by employing the representative volume element method and Voigt’s micromechanical homogenization scheme. The nonlinear mathematical model of the FG-panel is developed by incorporating Green-Lagrange type nonlinear strains in higher-order-midplane kinematics. The minimum potential energy principle is used to obtain the final form of the equilibrium equation for the multidirectional FG shell panel and further solved by using Picard’s iterative-based 2D-isoparametric finite element method via quadrilateral Lagrangian elements. The efficacy and robustness of the present model are checked by comparing its results with previously reported literature. Numerous examples are solved to analyze the impact of material parameters, such as volume fraction index and porosity index, and geometrical parameters, such as aspect ratio and support conditions, on the nonlinear deformation behavior of multidirectional FG shell panels. In addition, parametric optimization is carried out to minimize the flexural response by using the response surface methodology and, hence, determining the optimal values of multidirectional porous FG-panel. The results demonstrate that, within the defined ranges of FG-panel, lower values of porosity index and volume fraction index yield lesser deflection.

3D Textile Reinforced Cement (TRC) composites with integrated synthetic microfibres: Evaluation of mechanical response and crack formation in bending

This study explores the integration of short synthetic microfibres into 3D Textile Reinforced Cement (3D TRC) composites to achieve enhanced flexural capacity and improved crack control. The homogeneous distribution of microfibres within 3D TRCs was a challenge unaddressed in the current state of the art. The influence of the added microfibres on the bending behaviour and crack formation of the 3D TRCs was evaluated, along with the effect of crucial parameters such as the microfibre type (PP/PVA), length (3 mm/6 mm/8 mm) and content (0.5 %/0.7 %/1.0 %). Microfibre-enhanced 3D TRCs demonstrated a higher ultimate load and post-cracking stiffness, as well as more and narrower cracks.

From seasonal field study to surrogate modeling: Investigating the biomechanical dynamics of Elymus sp. in salt marshes

AbstractSalt marshes have been studied in the context of ecosystem services they can provide for coastal protection. In this study, monthly field campaigns focusing on Elymus spp. and its biomechanical properties were conducted from December 2021 to December 2022 on the German Barrier Island Spiekeroog. A total of 1390 specimens were investigated to determine their growth length, out of which 418 specimens were investigated mechanically with three‐point bending tests to determine their biomechanical properties. To evaluate the interaction of hydraulic loads and vegetation, the challenge of modeling biomechanical plant properties to scale is addressed by using resin 3D printing with flexible material, while focusing on the materials mechanical properties. Based on the field data acquired and additional literature (adding up to 1959 measurements), a cylindrical plant model with an outer diameter of (scale 1 : 1) was developed. It was manufactured mixing two resin components with varying volume ratios resulting in surrogates with different flexural stiffnesses. The surrogates were characterized using three‐point bending tests and image analysis of their bending behavior when subjected to currents between 0.4 and 1.2 m/s. With the average Young's modulus ranging from 8.45 to 1708.42 MPa, the bending angle varies from 0° to 77.4° displaying the influence of material stiffness and flow velocity. Applying the Cauchy scaling law, this study shows that resin 3D printing can be used to model Elymus sp. with respect to its biomechanical properties allowing for seasonally independent physical laboratory experiments with plant models.

A multiscale scheme for homogenization to characterize the flexural performances of injection molded short glass fiber reinforced polyether ether ketone composites

AbstractThe characterization of the flexural performances of short glass fiber reinforced polyether‐ether‐ketone (SGFR‐PEEK) composites fabricated by injection molding is a crucial and challenging task due to the process‐induced fiber orientation at different locations, resulting layered shell‐core‐shell microstructures and exhibiting large variations in mechanical performances. This article proposes a method for predicting the bending performance of SGFR‐PEEK and indicates the influence of fiber orientation on its bending behavior. This article reports a new scheme that combines multiscale homogenization with periodic microstructures and presents an experimental investigation of the flexural properties of SGFR‐PEEK composites. The distributions of fiber orientation through the thickness extracted from the micro‐computed tomography (μCT) were analyzed and reproduced with a layered skin‐shell‐core structure along the thickness at meso‐scale finite element model within representative volume elements (RVEs) of the macroscopic composites. Then, the effective properties of the RVEs were predicted using the homogenization method with the periodic boundary condition. The elastic modulus of skin‐shell‐core layers in the direction of flow are 4260.51, 4541.27, 4628.52, and 4630.84 MPa, respectively. The classical laminate theory (CLT) and the second homogenization implementation were then utilized in conjunction with the obtained mechanical properties of RVEs to predict the effective macrostructural behavior. The flexural modulus of the composite material was determined to be 5448.7 MPa through a three‐point bending test. The results obtained through lamination plate reinforcement theory and finite element simulation were 5887.4 and 5785.9 MPa, respectively, showing good agreement with the experimental findings. It is shown that the proposed multiscale scheme yields satisfactory agreement with experimental measurements. In addition, the effect of layered skin‐shell‐core microstructures on the flexural behavior was discussed.Highlights RVEs of layered shell‐core‐shell microstructures were generated with specified fiber orientations. The homogenization scheme with the periodic boundary condition was adopted to accurately predict each layer mechanical properties. The proposed multiscale scheme was compared with experimental results and yielded satisfactory predictions. The effect of layered skin‐shell‐core microstructures on the flexural behavior was thoroughly studied by the multiscale analytical approach.

Comparison of the Bending Behavior of Cylindrically Shaped Lattice Specimens with Radially and Orthogonally Arranged Cells Made of ABS.

The article deals with the comparison of the bending behavior of cylindrical lattice samples with radially and orthogonally arranged cells made of ABS material. The structures were designed in PTC Creo Parametric 8 software, while four types of lattice structures were evaluated: Rhombus, Cuboidal BCC, Octagon, and Starry, in three material volume fractions: 44, 57, and 70%, together with tubular and rod-shaped samples. The Fused Filament Fabrication (FFF) technique was chosen for the production of ABS plastic samples. Based on the bending tests, the dependences of the force on the deflection were recorded and the obtained data were statistically processed to identify outliers using the Grubbs test. The maximum stresses were calculated and the dependences of the stresses on the volume fractions were plotted. Along with energy absorption, ductility indices were also specified. Although the Rhombus structure appears to be the best based on the ductility indices obtained, on the other hand, the structure showed the lowest values of bending stresses (in the range from 10.6 to 12.6 MPa for volume fractions ranging from 44 to 70%, respectively). Therefore, from a synergic point of view of both factors, stress and ductility, the Starry structure exhibits the best flexural properties among those investigated.