Bending Behavior Research Articles

A numerical study on bending behavior of sandwich beam with novel auxetic honeycomb core

To further improve the load-bearing capability and anti-impact properties of the auxetic structure, a novel enhanced auxetic honeycomb core (NEH) was introduced, and the bending resistance and crashworthiness of this sandwich beam (NEH-SWB) were analyzed through numerical simulation. First, bending tests on sandwich beams under different loading situations revealed that NEH-SWB was more susceptible to impact damage in three-point bending situations than those under four-point bending, and the influence of structural parameters were more pronounced. In addition, the impact of load position and structural parameters on the bending response and deformation pattern of NEH-SWB were investigated. NEH-SWB exhibited superior bending resistance when the punch was located in the S position. Furthermore, increasing the panel thickness and altering the panel thickness configuration both contributed to improving the flexural resistance of NEH-SWBs. At a certain mass, the configuration with T f / T b > 1 exhibited better bending resistance. Meanwhile, increasing both the cell angle (θ) and wall thickness-to-length ratio (t/l) enhanced load-carrying capability and energy absorption of NEH-SWB. Subsequently, further analysis showed that NEH had better bending performance compared to cell structures with reentrant (RH), star-shaped (SSH), and reentrant-star (RSH) honeycombs. Finally, the complex proportion assessment method was employed to examine the significance of structural parameters regarding the flexural behavior of the NEH-SWB. It was concluded that increasing the t/l value could be the best solution to enhance the bending performance of the NEH-SWB.

A Four-Variable Shear Deformation Theory for the Static Analysis of FG Sandwich Plates with Different Porosity Models

This study is centered on examining the static bending behavior of sandwich plates featuring functionally graded materials, specifically addressing distinct representations of porosity distribution across their thickness. The composition of the sandwich plate involves a ceramic core and two face sheets with functionally graded properties. Mechanical loads with a sinusoidal distribution are applied to the sandwich plate, and a four-variable shear deformation theory is employed to establish the displacement field. Notably, this theory involves only four unknowns, distinguishing it from alternative shear deformation theories. Equilibrium equations are derived using the virtual work concept, and Navier’s method is applied to obtain the solution. The study addresses the impact of varying porosities, inhomogeneity parameters, aspect ratios, and side-to-thickness ratios on the static bending behavior of the sandwich plates. The influence of various porosities, inhomogeneity parameter, aspect ratio, and side-to-thickness ratio of the sandwich plates are explored and compared in the context of static bending behavior. The three porosity distributions are compared in terms of their influence on the bending behavior of the sandwich plate. The findings indicate that a higher porosity causes larger deflections and Model A has the highest central deflection. Adopting the four-variable shear deformation theory demonstrated its validity since the results were similar to those obtained in the literature. Several important findings have been found, which could be useful in the construction and application of FG sandwich structures. Examples of comparison will be discussed to support the existing theory’s accuracy. Further findings are presented to serve as benchmarks for comparison.

A Hot‐Stamped Medium‐Mn Steel with Superior Strength–Ductility–Bendability Combination and Thin Oxidation Layer

A hot‐stamped medium‐Mn steel containing 3.84 wt% Mn is designed for the manufacture of hot‐stamped automotive components. The effects of intercritical temperatures employed for hot forming on the microstructure, tensile properties, and three‐point bending behaviors are investigated. The result shows that the microstructure can be controlled by intercritical temperatures, leading to different phase fractions of martensite, retained austenite, and ferrite in the steels. Besides, the tensile strength increases with increasing intercritical temperature, while both the total elongation and the bending angle show reverse change trend, which are related to the various phase fractions and the different transformation‐induced plasticity effects during deformation. Importantly, the medium‐Mn steel subjected to heat treatment at 800 °C possesses tensile strength of 1535 MPa, total elongation of 13.8%, and bending angle of ≈56°. Therefore, its total elongation is significantly higher than hot‐stamped 22MnB5 steel under the same tensile strength grade, and the bending angle of the former is close to the latter. Moreover, the thickness of oxidation layer on the medium‐Mn steel is only ≈3.5 μm after heat treatment at 800 °C, much thinner than the ≈57 μm‐thick oxidation layer on the 22MnB5 steel after austenitizing at 930 °C.

Development and Analysis of an Origami-Based Elastomeric Actuator and Soft Gripper Control with Machine Learning and EMG Sensors.

This study investigates the characteristics of a novel origami-based, elastomeric actuator and a soft gripper, which are controlled by hand gestures that are recognized through machine learning algorithms. The lightweight paper-elastomer structure employed in this research exhibits distinct actuation features in four key areas: (1) It requires approximately 20% less pressure for the same bending amplitude compared to pneumatic network actuators (Pneu-Net) of equivalent weight, and even less pressure compared to other actuators with non-linear bending behavior; (2) The control of the device is examined by validating the relationship between pressure and the bending angle, as well as the interaction force and pressure at a fixed bending angle; (3) A soft robotic gripper comprising three actuators is designed. Enveloping and pinch grasping experiments are conducted on various shapes, which demonstrate the gripper's potential in handling a wide range of objects for numerous applications; and (4) A gesture recognition algorithm is developed to control the gripper using electromyogram (EMG) signals from the user's muscles.

Free vibration and static analysis of sandwich composite plate with auxetic core and GPLRC facing sheets in hygrothermal environment

The main objective of this study is to investigate the vibration and static analysis of a sandwich composite plate in the hygrothermal environment. The plate consists of three layers such as an Aluminum auxetic core and Graphene platelet-reinforced composite (GPLRC) facing sheets. Based on the Halpin-Tsai theory and Gibson's model, the macro mechanical properties of facing sheets and auxetic core are derived. Via Reddy's third-order shear deformation theory (TSDT), the equations of motion of the sandwich plate are obtained and solved by both Navier and the generalized differential quadrature method (GDQM). The current formulation is validated by comparing the numerical results with those that are reported in the literature. Finally, the influence of different parameters such as the inclined angle of auxetic cells, thickness to the length, and core to total thickness on the natural frequencies, deflection and stresses of the sandwich plate, is examined. Even though some studies have been conducted to investigate the bending or vibration behavior of sandwich structures with negative Poisson's ratio (NPR) cores, the bending and vibration behavior of such structures in the hygrothermal environment is remained unexplored. Additionally, the analysis of stress component variations along the thickness of the plate was a novel feature that has not been addressed in prior studies on the similar structure.

Single Curvature Bending of Structural Stitched Textile Reinforcements Part I: Experimental Work

Aerospace structural components made from polymer matrix composites (PMCs) offer numerous advantages. Their high stiffness and high strength combined with low densities enable lower fuel consumption coupled with higher payloads. As a result, PMCs provide an important economic advantage over typical metallic airframes. Textile reinforcements for PMCs are made by assembling reinforcement fibres, typically carbon. Then, the textile reinforcements are typically cut into smaller pieces, stacked, draped and assembled into a dry assembly called a preform, the shape of which generally approaches that of the PMC part to be made. This manufacturing process is labour intensive and expensive.Novel thick, net-shape, drapable, high fibre volume fraction (vf) textile reinforcements used toward manufacturing aerospace PMCs are being developed at the University of Ottawa. The technology enables the manufacturing of flat, drapable multilayered near net-shape preforms. The bending and in-plane shear behaviours of such novel thick reinforcement textiles was investigated to understand and define the behaviour of such thick fabric reinforcements when formed into required shapes. A bending apparatus was developed for investigating the bending behaviour of these novel thick reinforcement fabrics.

In-plane and out-of-plane one-way vertical bending behavior interaction analysis of unreinforced masonry walls with newly developed load capacity interaction curve

The structural behavior of unreinforced masonry (URM) walls under in-plane (IP) or out-of-plane (OOP) loading in masonry buildings has been extensively investigated in the public literature. However, studies focusing on the URM walls subjected to concurrent IP and OOP loadings are limited. Neglecting IP and OOP interaction effects may lead to unsafe design practices. As such, this study conducts a comprehensive numerical investigation into the behavior of URM walls under combined IP and OOP loading, focusing on the influences of aspect ratio (i.e., height-to-length ratio), slenderness ratio (i.e., height-to-thickness ratio), and pre-compression load levels. To capture the possible failure modes of URM walls under various loading scenarios, the simplified micro modeling approach is employed. The analysis results indicate that the presence of OOP loading leads to a substantial reduction in IP capacities. Longer walls, characterized by smaller AR, exhibit more pronounced IP and OOP interaction effects. Additionally, highly slender walls show significant additional moments due to second-order effects under OOP loading, thereby negatively affecting the IP capacity. Low-level pre-compression loads are beneficial in diminishing capacity interaction effects, while high pre-compression loads exert a negative influence. To facilitate the consideration of IP and OOP capacity interaction effects in an efficient manner, a simplified analytical model is developed through curve fitting, in which the effects of aspect ratio, slenderness ratio, and pre-compression load are incorporated.

A novel fiber-reinforced polymer rope: Concept design and experimental evaluation

The present study proposes using a twisted rope with flexible fiber-reinforced polymers (FRPs) instead of wire rope and synthetic rope in environments requiring high load-bearing capacity and corrosion resistance. Resin toughening modification was conducted to manufacture flexible FRPs, and experimental evaluations were performed to assess the tensile and flexural properties of the impregnated fiber bundles (IFBs), as well as the tensile behaviors of the seven-IFB strands and the seven-strand ropes. The results demonstrated that the modified epoxy resin exhibited a decrease in both strength and elastic modulus, while its ductility was enhanced. Tensile and bending experiments confirmed that incorporating an additional 10% of Qishi toughener (QS-VA-3) was the optimal choice for producing low-modulus and high-toughness resins. Although the tensile properties of resin modified IFBs may show a slight reduction, their repeated bending behavior can be significantly improved. The tensile load-displacement curves of the FRP strand and rope displayed a linear increasing trend and experienced intermediate fracture failure, resembling that observed in IFBs. Furthermore, it was found that the tensile strength and elastic modulus of the strand decreased with an increase in lay length. The secondary twisting can enhance the tensile behavior of ropes compared to strands with equivalent lay lengths.

Energy absorption characteristics of stepped multi-cell columns subjected to transverse loading

Automotive bumper beam is a vital component that shields passenger and vehicle from harm and damage generated by catastrophic collapse. Previous investigations on its bending behavior have largely concentrated on multi-cell tubes with the same length, whereas stepped multi-cell structures have received less attention. In this paper, a novel stepped multi-cell configuration is proposed to improve the energy absorption characteristics of thin-walled structures under transverse loading. The finite element method is employed to analyze the crushing behaviors of the stepped multi-cell tubes. The numerical results reveal that the stepped multi-cell structures (SM2 to SM5) can reduce the initial peak force by 23.44–45.91% while increasing the energy absorption capacity, crush load efficiency, and specific energy absorption by 5.87–29.51, 38.29–139.45, and 5.87–29.51%, respectively, when compared to a conventional square tube (M1). In addition, the effects of wall thickness, section width, load angle, punch radius, and punch shape on the bending behaviors and energy absorption characteristics are examined. The results indicate that these factors have a considerable influence on the deformation features of M1 and SM2, which leads to a significant reduction in their bending energy absorption characteristics. These variables have no influence on the deformation modes of SM3, SM4, and SM5, and they present local indentation deformation with a high energy absorption efficiency. Increasing the number of layers improves the comprehensive performance of stepped multi-cell tubes, with SM5 exhibiting the best energy absorption characteristics under transverse loading.

Kinetic module in bimetal: A biomimetic approach adapting the kinetic behavior of bimetal for adaptive Façades

This research is bioinspired by the leaf-rolling mechanism observed in Ammophila arenaria grass. This organism exhibits a bending behavior in response to adverse environmental conditions. We used bimetal, a smart material composed of two layers with distinct expansion coefficients, providing a bending behavior triggered by heat, mimicking the organism's natural response. Following the A. arenaria’s morphology, we applied creases on the bimetal's active layer. These creases influence the movement behavior of the bimetal, causing it to open when heated and close when cooled (opposite to the behavior observed in the material without creases). This study focuses on investigating the behavior of creases on the bimetal to propose a kinetic façade module responsive to changes in environmental temperature — the Bimetal Biomodule. We conducted exploratory studies to introduce creases on the bimetal surface, employing both handmade creases and 3D-printed matrix for stamping. We evaluated the response of the biomodule samples to temperature variations. Our findings indicate that interspersed creasing patterns, associated with the absence of creases at the material edges, influence the bimetal's behavior, offering control over material responsiveness beyond its properties. Prototypes and tests demonstrated the biomodules’ potential for self-shading applications on façades without electrical power or any mechanical device.

Galactoseismology in cosmological simulations

Context. Complex models recently became available for studying the dynamics of disk galaxies such as the Milky Way (MW). These models include the global dynamics from dwarf satellite galaxies, dark matter halo structure, gas infall, and stellar disks in a cosmological context. Aims. We use a MW model from a suite of high-resolution hydrodynamical cosmological simulations named GARROTXA to establish the relationship between the vertical disturbances seen in its galactic disk and multiple perturbations from the dark matter halo, satellites, and gas. Methods. We calculated the bending modes in the galactic disk in the last 6 Gyr of evolution. We computed the vertical acceleration exerted by dark matter and gas in order to quantify the impact of these components on the disk, and compared this with the bending behavior with Fourier analysis. Results. We find complex bending patterns at different radii and times, such as an inner retrograde mode with high frequency and an outer slower retrograde mode excited at different times. The amplitudes of these bending modes are highest during the early stages of formation of the thin disk (20 km s−1) and reach up to 8.5 km s−1 in the late disk evolution. We find that the infall of satellite galaxies leads to a tilt of the disk, and produces strong anisotropic gas accretion with a misalignment of 8° with subsequent star formation events and supernovae, creating significant vertical accelerations on the disk plane. The misalignment between the disk and the inner stellar and dark matter triaxial structure, which formed during the ancient assembly of the galaxy, also leads to a strong vertical acceleration of the stars. We also find dark matter subhalos that temporally coincide with the appearance of bending waves in certain periods. Conclusions. We conclude that several agents trigger the bending of the stellar disk and its phase spirals in this simulation, including satellite galaxies, dark subhalos, misaligned gaseous structures, and the inner dark matter profile. These phenomena coexist and influence each other, sometimes making it challenging to establish direct causality.

Characterization of the deformation behavior and microstructure evolution in laser bending of TC4 titanium alloy heavy plate

A new plastic processing method for laser bending of TC4 titanium alloy heavy plates was developed in this work. Different from previous studies, the thickness of the plates in this work reached 6 and 12 mm. High-energy laser beam was applied on the surface of the TC4 titanium alloy heavy plate, resulting in thermal stress on the surface of the plate and causing bending deformation. The microstructure and mechanical properties of the bended plates were investigated. A finite element model was also developed to simulate the laser-assisted bending process of the TC4 titanium alloy heavy plate. The microstructure observation indicates that the original α + β worm-like microstructure changed to basket-weave microstructure composed of α′ phase of acicular martensite after laser bending. This microstructure with high densities of dislocation and twinning played an important role in grain boundary strengthening. Therefore, the hardness of the center of the heat-affected zone > the hardness of the base metal > the hardness of the edge of the heat-affected zone after bending. The tensile strength of the heat-affected zone is not significantly different from that of the base metal, but the tensile elongation is slightly lower than that of the base metal and its plasticity is lower. The simulation implies that temperature gradients in the normal direction caused by laser scanning can stimulate a horizontal partial stress σx. The variation of σx causes the plate form a bending angle after laser scanning.

Investigation of Flexural Bearing Behavior of Corroded RC Strengthened with U-Type TRC.

In this study, the flexural bearing behavior of corroded reinforced concrete (RC) beams reinforced with U-type Textile Reinforced Concrete (TRC) was investigated using a four-point bending loading method. Nine test beams were produced: one original beam, three RC beams with corrosion alone, and five corroded beams strengthened with U-type TRC. The analysis focuses on assessing the impacts of the steel corrosion degree and the number of textile layers on various aspects of the bending behavior, such as failure modes, bearing capacity, and load displacement curves, in U-type TRC-strengthened corroded beams. The experimental results revealed three distinct failure modes in the U-type TRC-strengthened corroded beams. TRC effectively enhanced the bearing capacity. With sufficient textile layers, it can be restored to the level of the original RC beams. Moreover, in the cases of severe corrosion in RC beams, the bearing capacity increased more significantly. The TRC also enhanced the ductility. Finally, a calculation equation for the ultimate bearing capacity of U-type TRC-strengthened corroded beams was presented and validated, demonstrating consistent alignment with the experimental data.

Experimental investigation of ultrasonic assisted coating on three-point bending behavior of 3D printed polymeric bone plates for biomedical applications

3D printed Poly Lactic Acid (PLA) bone plates exhibit limited three-point bending strength, restricting their viability in biomedical applications. The application of polydopamine (PDM) enhances the three-point bending strength by undergoing covalent interactions with PLA molecular structure. However, the heavy nature of PDM particles leads to settling at the container base at higher coating solution concentrations. This study investigates the impact of ultrasonic-assisted coating parameters on the three-point bending strength. Utilizing Response Surface Methodology (RSM) for statistical modeling, the study examines the influence of ultrasonic vibration power (UP), coating solution concentration (CC), and submersion time (TIME). RSM optimization recommended 100 % UP, 6 mg/ml CC, and 150 min TIME, resulting in maximum three-point bending strength of 83.295 MPa. Microscopic images from the comparative analysis revealed non-uniform coating deposition with mean thickness of 6.153 µm under normal coating. In contrast, ultrasonic-assisted coating promoted uniform deposition with mean thickness of 18.05 µm. The results demonstrate that ultrasonic-assisted coating induces PDM particle collision, preventing settling at the container base, and enhances three-point bending strength by 7.27 % to 23.24 % compared to the normal coating condition. This study emphasizes on the potential of ultrasonic-assisted coating to overcome the limitations of direct immersion coating technique.

Experimental and numerical investigation of patch effect on the bending behavior for hat-shaped carbon fiber composite beams

Abstract In this study, reinforced composite panels with hat-shaped profile were produced from woven carbon fiber fabrics by vacuum infusion method. Holes were drilled on the crown surface of these panels and repaired with composite patches. The mechanical behavior was examined by performing a three-point bending test on the obtained patched and unpatched specimens. The contribution of the repair to the failure load of the damaged specimens under bending load has been clearly determined. In the numerical part, Hashin damage criterion was used for the beginning of damage. For damage progression, both Continuum Damage Mechanics and Material Property Degradation methods were preferred and compared. In the analysis carried out using the finite element package program Workbench, the cohesive zone model (CZM) was added to the model and its effect on the damage behavior and load of the composite structure was determined. As a result of the experiments and analyses, it was seen that the maximum contact force of the specimens under the bending load decreased by 29.8 % by increasing the number of holes on the specimen surface from 1 to 3. The maximum contact force was determined to increase by 18.52 % due to repairing the three-hole specimens with a patch.

High-pressure study on calcium azide (Ca(N3)2): the bending of the azide ions stabilizes the structure

Abstract The high-pressure structure and elastic properties of calcium azide (Ca(N3)2) were investigated using in-situ high-pressure X-ray diffraction and Raman scattering up to 54 GPa and 19 GPa, respectively. The compressibility of Ca(N3)2 changed as the pressure increased, and no phase transition occurred within the pressure from ambient pressure up to 54 GPa. The measured zero-pressure bulk modulus of Ca(N3)2 is higher than that of other alkali metal azides, due to differences in the ionic character of their metal-azide bonds. Using CASTEP, all vibration modes of Ca(N3)2 were accurately identified in the vibrational spectrum at ambient pressure. In the high-pressure vibration study, several external modes(ext.) and internal bending modes(ν2) of azide anions(N3 -) softened up to ~7 GPa and then hardened beyond that pressure. This evidence is consistent with the variation observed in the FE -fE data analyzed from the XRD result, where the slope of the curve changes at 7.1 GPa. The main behaviors under pressure are the alternating compression, rotation, and bending of N3 - ions. The bending behavior makes the structure of Ca(N3)2 more stable under pressure.

Bending and Vibration Behaviour of CLT-Steel Composite Beams

A strengthening of cross-laminated timber (CLT) by a composite effect with steel girders can widen the application of CLT ceilings to spans over 8 m. Most possible shear connectors are not stiff enough to ensure a completely rigid composite. At present, it has not been sufficiently clarified how the elastic bending behaviour is affected by the influences of the flexibility of continuously and discontinuously shear connectors, the number of transverse layers of the CLT and the span width. Thus, 4-point bending tests and vibration tests were performed with different cross-section configurations and two different shear connectors in continuous and discontinuous spacing in spans of 8.10 and 10.80 m. To date, no comparable bending tests have been carried out in these spans, with more than five CLT-layers and discontinuously arranged shear connectors. The composite beams deformed linear-elastically until the yield strength of the steel was reached. The composite effect increased the elastic bending stiffness up to twofold compared to no composite. Increasing the span resulted in a higher bending stiffnesses. The elastic bending stiffness of the composite beams with shear studs was significantly lower than with fully threaded screws. For a worthwhile composite effect, both materials should contribute a balanced share of the stiffness. A larger share of the CLT in the bending stiffness compared to the steel girder created a higher elastic limit load capacity but an equivalent bending stiffness. It is necessary to discuss which cross-sectional configurations are appropriate in terms of load bearing capacity, economic efficiency and sustainability. To assess the practical application potential in spans between 8 and 12 m, the tests were additionally evaluated for the equivalent load level for the serviceability limit state of office or industrial buildings. For spans of 8.10 m, the limits according to EC5 for the initial deflection of L/300 and fundamental frequency of 8 Hz can be met. For spans of 10.80 m, only less strict deflection limits are achieved. However, by increasing the degree of composite through more shear connectors, compliance with the limit values mentioned could already be possible with the cross-sections tested. In case of fire, it may be sufficient to consider only the CLT with the reduced cross-section method (EN 1995-1-2) for load transfer, even for longer fire durations.

Single Curvature Bending Results of Structural Stitched Textile Reinforcements Part II: Quantitative Analysis Using Taguchi Method

A Novel non-crimp dry thick fabric was manufactured at the University of Ottawa advanced preforming technology (uOttawa fabric) to cover the growing need for such thick preforms in the aerospace applications. The bending behavior was investigated using significant numbers of tests performed with a new bending apparatus designed and manufactured at University of Ottawa.This research paper was aimed to analyze the bending results obtained for samples made from the new uOttawa fabric and samples made from an industrial fabric using a statistical method celled Taguchi method. The Taguchi analysis highlights the most parameters having the stronger effects on testing. The main parameters investigated in bending were the type of fabric, the thickness, yarn orientations, fibre volume fraction and bending cycles. Two plans were used to investigate which parameters have strong effect on bending moment. The Taguchi analysis revealed that the type of fabric, number of cycles and fibre volume fraction have the largest effect on bending behavior of these fabrics.

Large Deflection Geometrically Nonlinear Bending of Porous Nanocomposite Cylindrical Panels on Elastic Foundation

Large deflection nonlinear bending of functionally graded (FG) porous cylindrical panels reinforced with graphene platelets (GPLs) on a Pasternak-type elastic foundation is examined by developing a reliable and effective 2D meshfree-based nonlinear numerical method. The large displacement field is express by the first-order shear deformation theory (FSDT) and the von Kármán nonlinearity, and approximated by 2D natural element method (NEM) in conjunction with the stabilized MITC3+ shell concept and the shell surface–rectangular grid geometry transformation. The nonlinear simultaneous equations are solved by a load incremental Newton–Raphson scheme. The developed nonlinear numerical method is justified from by comparing with the reference solutions, and the load–deflection and bending moment of FG-GPLRC porous cylindrical panels on elastic foundation are scrutinizingly examined. Four different symmetric GPL distribution patters (except for FG-Λ) and three different symmetric porosity distributions are considered and their combined effects on the nonlinear bending behavior are investigated, as well as the effects of foundation stiffness and GPL amount. Also, the results are compared with those of FG CNT-reinforced porous cylindrical panels.

Negative bending behavior of web-embedded U-shaped steel-concrete composite beams

This paper discusses the negative bending behavior of a new type of web-embedded U-shaped steel-concrete composite beams (WUSCBs). Considering the installation of web-embedded shear connectors, a negative bending moment test was performed on seven WUSCB specimens. The web-embedded shear connectors in the WUSCB are shown to have good shear connection performance and maintain the overall function of WUSCBs. The failure progression of the specimens is characterized by the cracking, yielding, and buckling loads of 0.22Pu, 0.79Pu, and 0.92Pu, respectively. Negative bending failure was observed in the WUSCBs, evidenced by the steel plate yielding and concrete slab cracking. The WUSCBs were found to have good ductility and deformability under negative bending. A finite element model was established to validate the experimental results. The calculation methods for negative bending capacity and effective flange width are proposed; and the calculated results are in good agreement with the test results. A suggested value of moment modulation at the end of continuous beam is proposed.