Bending Capability Research Articles

Bending response and energy absorption of sandwich beams with combined reinforced auxetic honeycomb core

This study introduces a reinforced star-shaped auxetic honeycomb (RSSAH) sandwich beam, enhanced with hollow thin-walled tubes to improve bending resistance and energy absorption performance. The bending performance of the RSSAH is systematically investigated through quasi-static three-point bending tests and finite element numerical simulations. The findings suggest that when subjected to mid-span stress, the RSSAH displays both localized indentation and overall bending deformation, accompanied by notable negative Poisson’s ratio (NPR) impact under bending loads. Parametric studies are undertaken by numerical simulations to investigate the impact of compression position, auxetic angle, and face sheet thickness on the bending mode of the auxetic honeycomb sandwich beam. The analysis shows that the RSSAH can exhibit excellent bending performance and, at one of the compression positions, displays double-plateau stress characteristics. It is also found that altering key geometric parameters, such as the auxetic angle and panel thickness ratio, can greatly improve the bending capabilities of the RSSAH, achieving stable plastic deformation and high energy absorption. Finally, compared to star-triangle honeycomb (STH) sandwich beam, traditional reentrant honeycomb (RH) sandwich beam and star-shaped auxetic honeycomb (SSAH) sandwich beam, the RSSAH demonstrates superior bending performance and energy absorption capacity. This study offers insights and references for the development of innovative reinforced auxetic honeycomb sandwich beams.

Rapid 3D printing of electro-active hydrogels

Electroactive hydrogels (EAH) have gained prominence for their unique ability to change shape or size under an electric field, finding applications in biosensors and soft actuators. This study focuses on a tunnelable EAH tailored for high-resolution 3D printing via the micro continuous liquid interface production (µCLIP) process. The resin formulations mainly involve acrylic acid (AA) and 4-hydroxybutyl acrylate (4-HBA). AA, with its carboxyl groups, introduces electroactuation, generating osmotic pressure in the hydrogel matrix. This results in swelling, inducing bending towards the cathode, accentuating the material’s responsiveness. In contrast, 4-HBA offers mechanical resilience, providing an elastic backbone, and ensuring the hydrogel’s applicability. Our results illustrate the hydrogel’s strength, flexibility, and bending capabilities across varied compositions and electric field strengths. Notably, the µCLIP process enabled the 3D printing of our EAH into sophisticated structures, like the lattice. The combination of AA’s electro-responsive traits with 4-HBA’s durability has birthed a material with vast practical implications. This study provides extended potential breakthroughs in soft robotics, wearable electronics, and medical devices, marking a significant stride in the realm of electroactive materials.

Kinematic analysis of engagement and bending capabilities of a point-of-care, incremental skeletal fixation plate bending system

The current standard of care for skeletal reconstruction surgery is to join skeletal disunions with fixation plates and these plates are most commonly fit to bones through manual bending. The bending procedure is often performed in the surgical operating theatre with specialized pliers or, if available, lengthy pre-operative bending to fit a 3D printed skeletal model prepared on computer as part of a virtual surgical plan. Manual bending of fixation plates by eye or to a model can take considerable time. Repetitive bending at a single location can result in work hardening that increases the subsequent risk of fatigue failure. However, incremental forming systems may provide a solution to automatically bend fixation plates accurately, rapidly, and as little at any one location as possible. This paper is an investigation of the kinematics and manipulability of two versions of an incremental fixture plate bending system for Point of Care Manufacturing (POCM) of craniomaxillofacial (CMF) skeletal fixation hardware. The Automatic Plate Bender (APB) v1 is a minimal POCM system that is designed for simple straight plates with a constant incremental pitch. The APB v2 is a more complex POCM that is designed to accommodate a larger variety of standard plates. Kinematic and manipulability analysis demonstrate the engagement and bend classes that each system can accomplish, and identifies a critical singularity in the APB v2 mechanism. The paper concludes with two case studies in which a path planning algorithm uses a manipulability analysis to avoid singularities during incremental bending.

Bionic light-responsive hydrogel actuators with multiple-freedom motions in water environments

Soft actuators with biomimetic behavior have widely been utilized in intelligent robotics and artificial muscles. Herein, tannic acid (TA) non-covalently modified and γ-methacrylic trimethoxysilane (MPS) covalently modified MXene (MPS-TA-MXene) are incorporated into a poly(n-isopropylacrylamide-polyacrylamide) (PNIPAM-PAM) copolymer hydrogel to yield a light-responsive hydrogel nanocomposite, denoted as MNA. TA effectively preserves the surface characteristics of MXene while the double bonds in MPS form covalent bonding between MXene and PNIPAM-PAM copolymer, ensuring uniform dispersion of MPS-TA-MXene in MNA hydrogel. Under exposure to ultraviolet light, the resulting MNA hydrogel actuators with nematode- or starfish-shaped exhibit not only bending capabilities in various directions and angles but also demonstrate remarkable multiple-freedom rolling behavior in water environments due to their volume shrinkage induced by the phase transition of MNA hydrogel. Overall, the proposed simply assembled MNA hydrogel actuators with multiple and continuous bionic motions, distinguishing them from conventional single soft actuators limited to bending in one specific direction or performing a simple singular action of rolling, look promising for use in underwater exploration.

Effect of texture on bending behavior of Mg alloy sheets

The effect of Li elements on the microstructure and texture evolution of AZ31 alloy sheets during room-temperature three-point bending was investigated. The results showed that the conventional c-axis//ND basal texture of the extruded AZ31 sheet could be modified to a TD-elongated fiber texture with a 5 wt% Li addition. As a result, the room-temperature bendability of the Mg–3Al–5Li sheet was improved effectively, and this sheet showed a minimum bending radius of only 2 mm. The superior bendability exhibited surpasses the room-temperature bending capabilities commonly observed in the majority of commercial Mg alloys. The improvement in bendability of the Mg–3Al–5Li sheet was attributed to the TD-elongated texture distribution. This type of texture distribution may offer more effective deformation modes to alleviate thickness strain during bending in comparison to the texture in extruded AZ31 sheets. This study could provide insights into developing Mg alloys with high room-temperature bendability by tailoring texture distribution rather than texture weakening.

Soft crawling caterpillar driven by electrohydrodynamic pumps

AbstractSoft crawling robots are usually driven by bulky and complex external pneumatic or hydraulic actuators. In this work, we proposed a miniaturized soft crawling caterpillar based on electrohydrodynamic (EHD) pumps. The caterpillar was mainly composed of a flexible EHD pump for providing the driving force, an artificial muscle for performing the crawling, a fluid reservoir, and several stabilizers and auxiliary feet. To achieve better crawling performances for our caterpillar, the flow rate and pressure of the EHD pump were improved by using a curved electrode design. The electrode gap, electrode overlap length, channel height, electrode thickness, and electrode pair number of the EHD pump were further optimized for better performance. Compared with the EHD pumps with conventional straight electrodes, our EHD pump showed a 50% enhancement in driving pressure and a 60% increase in flow rate. The bending capability of the artificial muscles was also characterized, showing a maximum bending angle of over 50°. Then, the crawling ability of the soft crawling caterpillar is also tested. Finally, our caterpillar owns the advantages of simple fabrication, low‐cost, fast movement speed, and small footprint, which has robust and wide potential for practical use, especially over various terrains.

Behaviour and design of cold-formed high-strength steel built-up beams

The adoption of high-strength steel in the construction sector can provide potential advantages, such as supporting large-scale structures with small cross-sectional sizes leading to decreased self-weight and improved space availability. In this paper, detailed numerical investigations are presented to investigate the nonlinear behaviour of cold-formed high-strength steel (HSS) built-up beams subjected to in-plane flexure along with their bending moment capacities, deformed shapes, and moment-curvature curves. Finite element (FE) models incorporating the initial geometric imperfections of cold-formed sections and material nonlinearities were established and validated against the experiments presented in the literature by comparing the moment-curvature curves, deformed shape, and ultimate bending moment capacities. Following validation, the calibrated FE models were utilized to perform extensive parametric studies to generate further numerical data by varying three different parameters: cross-sectional yield strengths (S700, S900 and S1100), geometries (such that the local slenderness, λl values varied from 1.07 to 4.65) and cold-formed steel (CFS) sheet thicknesses (1.0, 1.5, 2.0, and 2.5 mm). The specimens considered in the present study were restrained to inhibit lateral-torsional buckling and demonstrated failure owing to local buckling. The applicability of the design principles for predicting bending capabilities was assessed using numerical data in accordance with direct strength method (DSM) of AISI codal provisions and continuous strength method (CSM). The obtained numerical results demonstrated that the existing standards lack precise design procedures for cold-formed HSS built-up members and additional research is still required to provide accurate design procedures. Therefore, an improved rational extension of DSM of AISI codal provisions and CSM is recommended to predict the ultimate bending moment resistance.

Light‐activated 3D printed fish‐like actuator

AbstractHydrogel‐based actuators are innovative materials that exhibit responsive and dynamic behavior in response to external stimuli, making them promising candidates for a wide range of applications in fields such as soft robotics. We employ 3D printing to create layered rectangles, using a passive ink composed of gelatin methacryloyl (GelMA) and an active ink consisting of GelMA and poly(N‐isopropylacrylamide) (PNIPAM). Our aim is to assess and compare the bending capabilities of these structures based on their layer arrangements in a buffer above the lower critical solution temperature. Therefore, an asymmetric rectangular structure is selected as the shape‐changing component in the tail of a 3D printed fish‐shaped hydrogel actuator. We show that gold nanostars integrated into the actuators serve as photothermal elements, enabling the fish tail to repeatedly bend when near infrared light is turned on and off. Our effort illustrates the potential of combining 3D printing, responsive hydrogels and photothermal elements with near infrared light towards soft robotic applications. This combination yields actuators capable of shape‐shifting without requiring localized light or transitioning between environments with varying temperatures.

Flexible organic crystal with dual mechanical bending capabilities and optical waveguiding directionality

The study of organic luminescent crystal material has become a hot topic in the field of flexible optoelectronics. In this context, we report a crystal of 2,5-dihydro-3,6-bis (pentanamine) dimethyl terephthalate, which exhibits the unique property of self-doping, coupled with dual mechanical bending capabilities. Notably, the crystal exhibits optical waveguide properties, which highlights its potential application in flexible optoelectronics. In this work, through a simple "self-doping” process and controlled morphology, we obtained the synthesis of high-quality bulk organic crystals of varied sizes that not only bend elastically but also bend plastically as the molecular layer undergoes slippage. Subsequent, analysis of the crystal structure was conducted to investigate the reason for its dual mechanical bending capabilities. Our findings suggested that the optical waveguide is not only available in linear shape, elastic bending shape, and plastic bending shape, but also in large-size flake crystals. More importantly, the propagation of light in this crystal is directional owing to the anisotropy of the crystals. It is also proven that organic crystals have the potential to be applied in advanced optoelectronic devices, offering the possibility of their application as directional waveguide materials.

Compact off-axis reflective optical system design combining freeform mirror and freeform detector

Minimizing system size and weight without sacrificing the desired imaging performance is a crucial and challenging goal in the design of off-axis optical systems. In this paper, we propose a design concept that combines freeform mirror and freeform detector to achieve more compact off-axis optical systems. Initially, by applying nodal aberration theory, the optimal focal surface shape for off-axis systems is demonstrated to be an off-axis paraboloid or even a freeform surface, rather than the commonly assumed spherical shape. Subsequently, we show the ability of the design concept to reduce off-axis system volume through a design example of a fast and wide-field off-axis three-mirror system. Results indicate that, under the same design parameters and imaging quality, the design with a freeform detector is 80% smaller than that with a flat detector in terms of volume. Finally, the bending capability of the freeform detector presented in this paper is ensured through finite element analysis, and its surface accuracy is achievable based on the current precision level of curved detector fabrication. The proposed design concept holds promise for application in planetary science, where the imaging performance of the instrument is highly required and the size and weight are strictly limited.

Development of smart materials with versatile bending capabilities using microcellular foaming process: influence of foaming and desorption time

Abstract Herein, a smart material with versatile bending capability is developed using a microcellular foaming process (MCPs). In contrast to previous hydrogel-based approaches, the bi-layered smart material is fabricated using typical thermoplastics, polyethylene terephthalate glycol (PETG) and polymethyl methacrylate (PMMA), to achieve shape deformation in response to thermal stimuli. Further, the theoretical model for bi-layered smart materials based on the modified Timoshenko’s model is employed to predict and comprehend this thermal response phenomenon. Due to the distinct foaming characteristics of the two polymers, a reversal in the bending direction is achieved by manipulating the foaming and desorption time. The length variation after foaming differs depending on the desorption time for each polymer. PMMA decreases in length after foaming, measuring 56.25 mm at a desorption time of 40 min and 53.16 mm at 80 min. On the other hand, PETG shows an increase in length after foaming, measuring 53.33 mm at 40 min and 58.25 mm at 80 min. Consequently, when the two polymers are bonded and foamed, bending occurs depending on the desorption time, and a reversal in the bending direction is observed at the critical desorption time of around 60 min. Based on this result, the folding direction of a five-leafed flower-shaped object is successfully altered under thermal stimuli. This innovative approach extends the category of smart materials beyond the hydrogels and showcases the potential of the MCPs for the creation of smart materials for various applications that require versatile shape changes in response to temperature.

Experimental investigation on adaptive grasping of a novel 3D-MSSPA gripper in complex space

Many achievements for soft grippers are made in the structure design and grasping of target objects. However, there are limited studies on grasping objects with different attributes by soft grippers with omnidirectional bending capabilities within environments containing obstacles. In this paper, drawing inspiration from the multi-segment structure of the biological finger, a 3D-multi-segment soft pneumatic actuator (3D-MSSPA) with a strong envelope and omnidirectional independent bending is designed and manufactured. Additionally, we developed a novel prototype for a soft gripper prototype. A quasi-static model is proposed to effectively describe the bending deformation of 3D-MSSPA. The experimental results show that, for an applied pressure of 40kPa, the single segment SPA achieves a maximum bending angle of 175.2°, aligning closely with the theoretical prediction. Furthermore, the omnidirectional bending ability of multi-segments is analyzed through the finite element method, and a position compensation method for gravity deviation is presented. Through experiments, the pressure fore and lifting force of the soft gripper are investigated, yielding maximum values of 11N and 4.08N, respectively. These results serve as a benchmark for the mass grasping range of the target objects. Finally, the experiments are conducted to demonstrate the soft gripper’s adaptive and flexible grasping capabilities for objects with varying attributes, in both free space and complex space with obstacles. These experiments showcase their ability to avoid obstacles, adaptively grasp objects, and their good envelope ability. The proposed 3D-MSSPA can provide good inspiration and reference for flexible applications, particularly in fields such as post-disaster rescue and rehabilitation medicine.

Bio-inspired soft robot with varied localized stiffness

Soft robots are a type of intelligent robot with high adaptability, and the majority of them are made from soft materials, so they are flexible and adaptable. The variable stiffness function of soft robots is crucial, as it can enhance the robot's adaptability, safety, and dependability. By adjusting the stiffness, the soft robot is able to maintain a stable motion state in a complex environment, reduce environmental interference, and perform human-like actions with improved target control. The elephant trunk served as inspiration for the way proposed in this study for modifying the soft robot's arm's stiffness. By changing the insertion scheme of the interference plate in a flexible manner, the robot arm can have variable bending capability, allowing it to complete a variety of work instructions given by humans and to satisfy a variety of work requirements.

Investigation of the Effect of the Force Arm on the Bending Capability of Prestressed Glulam Beam

Investigation of the Effect of the Force Arm on the Bending Capability of Prestressed Glulam Beam

Exploring bundle bamboo split technique in bending dendrocalamus asper for landscape structure

Bamboo is one of the fastest-growing natural construction materials and is locally available in most developing countries, including South America, Africa, and Asia. Bamboo is a “green gold” plant in the tropical forest. It is a fast-growing monocotyledon species belonging to the Gramineae family (Bambusoideae) and requires a short time for re-production. Bamboo’s physical strength provides builders from ancient times until today an opportunity to use bamboo as a natural and sustainable construction material for building houses and structures. Due to its capability to bend, bamboo is the most preferred material in vernacular construction and lately in Southeast Asia countries which borne new trend in building design. The built-environment professionals, namely landscape architects, architects, and engineers in Malaysia, still lack knowledge of bamboo, especially on bending capabilities, as one of the sustainable construction materials. Less concern was given to researching the capabilities of bamboo’s ability to bend, even though its strength is more than steel and provides various design opportunities compared to other sustainable materials. Different types of bamboo present different strength capacities. Therefore, the aims of this research is to compare and determine their strength capacity, bending criteria and species suitability for design and construction in Malaysia. This paper collects published literature on experimental studies on the different methods of Hot and Cold Bending Methods which allow bamboo to bend to suit designer needs and concentrate on Malaysian Dendrocalamus asper (Buluh Betung), which considered as tough and durable species, as the primary construction material for landscape structures. Bundle Bamboo Split (BBS), identified as one of the bending techniques adopted for an experimental project, using BBS of 0.8m radius, produces a prototype for a landscape structure. The findings indicate observation of works by a team of craftsmen trained by an expert in bamboo construction who used to produce bamboo structures from Bali, Indonesia, highlighted tools and procedures in bamboo construction. In short, this paper will also enhance the use of bamboo as an accessible, durable, creative and sustainable construction material that represents the local identity of Tropical Malaysia Landscape Architecture.

In-situ Mg-Al LDH infused lignin-derived laser scribed graphene for facilitated ion transport in flexible supercapacitor application

BackgroundInnovations in the synthesis of hybrid materials have led to technology advancement of the microsupercapacitor. Delaminated layered double hydroxide (LDH) reduces self-agglomeration and increases energy density in graphene-based supercapacitors. The incorporation of delaminated LDH with oil palm lignin derived laser scribed graphene in neutral PAAS/K2SO4 gel electrolyte for flexible microsupercapacitor applications was investigated. MethodVarious concentrations of positively charged sucrose-delaminated Mg-Al LDH nanosheets produced through the coprecipitation method were hybridised with negatively charged oil palm lignin-derived laser scribed graphene (L-LSG) through electrostatic interaction. Significant FindingsHybrid laser scribed graphene developed from delaminated Mg-Al LDH at a concentration of 10 gL−1 (L-LSG/D-MgAl-10) had the largest surface area of 49.335 m2g−1. The incorporation of Mg-Al LDH nanosheets on l-LSG were further validated by FESEM, TEM, XRD, Zeta potential and other characterizations. It also had the highest areal capacitance and energy density, measuring 40 mFcm−2 and 0.00296 mWhcm−2, respectively, at a current density of 0.08 mAcm−2. The fabricated microsupercapacitor has exceptional bending capabilities and capacitance retention of 89.2% after 5000 cycles. In summary, by inducing additional pseudocapacitance, delaminated Mg-Al LDH improved the overall effectiveness of the oil palm lignin derived graphene electrode compared to pristine graphene.

Deformation Characteristics of Three-Dimensional Spiral Soft Actuator Driven by Water Hydraulics for Underwater Manipulator.

The emergence of bionic soft robots has led to an increased demand for bionic soft actuating ends. In this study, a three-dimensional spiral water hydraulic soft actuator (3D-SWHSA), inspired by the winding action of an elephant's trunk, is proposed to provide a more targeted soft actuator catching method. The 3D-SWHSA is composed of multiple bending and twisting units (BATUs), which can produce winding deformation after being pressed. By using the principles of virtual work and integrating the Yeoh 3rd order model, a predictive model for winding was established to investigate the bending and twisting characteristics of BATUs with varying structural parameters through finite element simulation. Following the selection of an optimal set of structural parameters for the 3D-SWHSA, its bending and deformation capabilities were simulated using finite element analysis and subsequently validated experimentally. To validate its flexibility, adaptability, and biocompatibility, successful catching experiments were conducted in both air and underwater environments. Underwater organisms, including organisms with soft appearance such as starfish and sea cucumbers, and organisms with hard shell, such as sea snails and crabs, can also be caught harmlessly. In cases where a single 3D-SWHSA is insufficient for capturing objects with unstable centers of gravity or when the capture range is exceeded, the double 3D-SWHSAs can be utilized for cooperative winding. This study affirms the great potential of 3D-SWHSA in diverse marine applications, including but not limited to marine exploration, fishing, and operations.

Controlling a Below-the-Elbow Prosthetic Arm Using the Infinity Foot Controller

Nowadays there are various prosthetic arm designs in the literature, the market, and CAD design websites, with different shapes, sizes, and degrees of freedom. Only limited options are available for controlling such prostheses. Prosthetic arm users reported muscle fatigue and unreliability when using the market-dominated myoelectric sensors. This work presents the “Infinity Foot Controller” as a new approach to control a five-finger below-the-elbow prosthetic arm with wrist rotation and bending capabilities. This foot control system receives user input from a custom insole and a sensor-controller unit placed alongside the user’s shoe to perform various hand grips, gestures, and/or rotations. To demonstrate the new foot controller, a design of a 3D-printed below-the-elbow prosthetic arm, called the “Infinity Arm”, is presented. This arm is suitable for gripping relatively lightweight objects and making hand gestures. It includes a wrist actuation system that permits 120° wrist rotation and 70° wrist extension and flexion. It also includes a haptic feedback system that utilizes fingertip force sensors to relay a vibratory response in an armband placed on the user’s arm, giving the user a sense of touch. A proof-of-concept model was built to demonstrate the system and a testing procedure was proposed.

Mechanical properties of ply-lam cross-laminated timbers fabricated with lumber and plywood

The mechanical properties of four ply-lam cross-laminated timbers (CLTs) containing a plywood layer were compared with those of glued laminated timber (GLT) and CLT. The bending, out-of-plane shear, and compression strengths were highest in the GLT, followed by the ply-lam CLTs and CLT. The modulus of elasticity (MOE) values for the three studied ply-lam CLT samples were 1–2.5 GPa higher than GLT; however, the modulus of rupture (MOR) of all ply-lam CLTs was 7.3–18.8 MPa lower than GLT. The length of the plywood product is 2,440 mm, and longitudinal bonding is required to manufacture ply-lam CLTs of length > 3 m. The prediction of bending capabilities by shear analogy was compared with the bending properties when joints were included. The performances of all the pilot-scale ply-lam CLT samples exceeded the predicted bending performance standards for MOE (10 GPa) and MOR (30 MPa) All samples exceeded 10 GPa and 30 MPa, based on projected and experimental data.

Gripping performance of soft grippers with fingerprint-like surface texture for objects with slippery surfaces

Soft robots face challenges when gripping and manipulating objects in lubricated environments, and one of the key issues in medical lubrication conditions in particular. In this study, soft actuators with independent pneumatic driven DIP and PIP joints are designed and prepared based on the anatomy of human fingers. The soft actuators are used to mimic the tip pinch action of the index finger and thumb, achieving dexterous grasping postures adapted to daily life, primarily for fine operation tasks. The bending capability, thrusting force, and fatigue life of the soft actuators are tested. Furthermore, by mimicking the three common fingerprint patterns (i.e., whorls, loops, and arches), three macroscopic surface textures were designed and prepared on the surface of silicone rubber materials. Tribological properties of the surface textures are studied under medical lubrication conditions with hyaluronic acid solution as lubricant. Based on this, tip pinch gripping experiments are conducted on standard shape objects, common medical devices, and biological materials with surface mucus layer. The results showed that the surface of the soft actuators can fit well with the surface of the gripped objects, thereby achieving a larger contact area and enabling the gripping of standard items and common medical devices. Moreover, for biological materials with mucous layer of significant differences in physiological function, the weight that can be gripped is significantly higher than that of the gripper without surface texture.