Bent Shape Research Articles

Natural convection heat transfer from linearly, circularly and parabolically bent plates: A study of shape effect

In the present study natural convection heat transfer from three differently bent shapes (linear, circular, and parabolic) has been investigated numerically for laminar flow in the range of Ra from 103 to 106. The simulations are carried out for different orientations by varying X/L from 1 to 0.3 keeping the surface area same for all the shapes. The present numerical study is able to capture a complete and very interesting picture of temperature plume and flow field over the bent plates. From the numerical results, it has been observed that heat loss from an upward bent plate is more compared to a downward bent plate for all the shapes at same Ra. Parabolically bent plate is most effective in losing heat compared to a linearly and circularly bent plate of same area. There is an optimum X/L for maximum heat loss for bent plate; further bending the plate reduces heat transfer slightly. The effects of parameters like X/L, Ra on average Nu from the top and bottom surface, total heat transfer, skin friction coefficient, temperature plume, and flow field are shown in the study which would enrich the literature archive tremendously.

Programmable Fabrication of Submicrometer Bent Pillar Structures Enabled by a Photoreconfigurable Azopolymer.

Anisotropic small structures found throughout living nature have unique functionalities as seen by Gecko lizards. Here, we present a simple yet programmable method for fabricating anisotropic, submicrometer-sized bent pillar structures using photoreconfiguration of an azopolymer. A slant irradiation of a p-polarized light on the pillar structure of an azopolymer simply results in a bent pillar structure. By combining the field-gradient effect and directionality of photofluidization, control of the bending shape and the curvature is achieved. With the bent pillar patterned surface, anisotropic wetting and directional adhesion are demonstrated. Moreover, the bent pillar structures can be transferred to other polymers, highlighting the practical importance of this method. We believe that this pragmatic method to fabricate bent pillars can be used in a reliable manner for many applications requiring the systematic variation of a bent pillar structure.

Overheating in residential areas: role of reflected solar radiation

A method to assess positions, time of appearance and intensity of reflected from façades solar radiation fields as a source of overheating near the buildings is graphically interpreted towards urban large-scale variously orientated residential blocks. The study indicates quantitative relationships between the buildings total area of walls as reflecting surfaces and a corresponding area of overheating caused by the reflections, with a focus on arcuate or bent buildings shapes. Although the assessment is performed for a particular morphology of residential buildings typical of Chelyabinsk city and taking into account its geographic latitude (56 North), the procedure is easily applied anywhere and the results might be useful during the process of choosing a site development options.

Rectangular Cross Section Beams Calculation on the Stability of a Flat Bending Shape Taking into Account the Initial Imperfections

The article presents the derivation of the resolving equation for the calculation of lateral buckling of rectangular beams. When deriving the basic equation, the initial imperfections of the beam are taken into account, which are specified in the form of the eccentricity of the applied load, the initial deflection in the plane of least stiffness and the initial twist angle. The influence of initial imperfections on the process of beam stability loss is investigated.

Hybrid Jamming for Bioinspired Soft Robotic Fingers.

This article describes a novel design of bioinspired soft robotic fingers based upon hybrid jamming principle-integrated layer jamming and particle jamming. The finger combines a fiber-reinforced soft pneumatic actuator with a hybrid jamming substrate. Taking advantage of different characteristics of layer jamming and particle jamming, the substrate is designed with three chambers filled with layers (function as bones) and two chambers filled with particles (function as joints). The layer regions and particle regions are interlocked with each other to guarantee load transfer from the fixed finger end to fingertip. With the proposed design, the finger is endowed with bending shape control, as well as variable stiffness capabilities. Theoretical analysis is conducted to predict the stiffness variation of the proposed finger at different vacuum levels, and experimental tests are performed to evaluate the finger's shape control and stiffness tuning effectiveness. Experimental results show that the proposed finger can achieve 5.52 times stiffness enhancement at primary position. Finally, we fabricate a gripper and perform grasping demonstrations on several objects. Results show that the gripper is able to transfer between low stiffness state for adaptive grasping and high stiffness state for robust holding.

Mechanical Assembly of Thermo‐Responsive Polymer‐Based Untethered Shape‐Morphing Structures

AbstractShape‐morphing robotic structures can provide innovative approaches for various applications ranging from soft robotics to flexible electronics. However, the programmed deformation of direct‐3D printed polymer‐based structures cannot be separated from their subsequent conventional shape‐programming process. This work aims to simplify the fabrication process and demonstrates a rapid and adaptable approach for building stimulus‐responsive polymer‐based shape‐morphing structures of any shape. This is accomplished through mechanically assembling a set of identical self‐bending units in different patterns to form morphing structures using auxiliary hard connectors. A self‐bending unit fabricated by a 3D printing method can be actuated upon heating without the need for tethered power sources and is able to transform from a flat shape to a bending shape. This enables the assembled morphing‐structure to achieve the programmed integral shape without the need for a shape‐programming process. Differently assembled morphing structures used as independent robotic mechanisms are sequentially demonstrated with applications in biomimetic morphing structures, grasping mechanisms, and responsive electrical devices. This proposed approach based on a mechanical assembling method paves the way for rapid and simple prototyping of stimulus‐responsive polymer‐based shape‐morphing structures with arbitrary architectures for a variety of applications in deployable structures, bionic mechanisms, robotics, and flexible electronics.

Index for Wood Bending Shapes

家具部材の曲げ木製造において，近年増加している不良現象への対策が課題となるいま，樹種の選定基準になる物性や，曲げ木可能な材厚（s）と曲げ半径（r）の相関のような形状基準が求められている。本研究では蒸煮直後の木材を押し型曲げ試験に供して，樹種別の材特性と曲げたわみ量の関係を検討した。押し型曲げ試験で引張側側面に割れが多数見られたため，縦引張試験から破壊ひずみの限界 （εt（Max）） を算出した。また，木材にベンディングバンドを沿わせて曲げることで材上端部から中立軸までの距離（t）が長くなることを確認した。本実験結果から，引張試験の破壊ひずみを判断指標とする条件式 （s-t） / （r + t） < εt（Max） が有用であることを提案する。 なお，押し型曲げ試験の結果が良好であった条件でこの関係が満たされていたことを確認した。

Molecular Flexibility and Bend in Semi-Rigid Liquid Crystals: Implications for the Heliconical Nematic Ground State.

The NTB phase phases possess a local helical structure with a pitch length of a few nanometers and is typically exhibited by materials consisting of two rigid mesogenic units linked by a flexible oligomethylene spacer of odd parity, giving a bent shape. We report the synthesis and characterisation of two novel dimeric liquid crystals, and perform a computational study on 10 cyanobiphenyl dimers with varying linking groups, generating a large library of conformers for each compound; this allows us to present molecular bend angles as probability weighted averages of many conformers, rather than use a single conformer. We validate conformer libraries by comparison of interproton distances with those obtained from solution‐based 1D 1H NOESY NMR, finding good agreement between experiment and computational work. Conversely, we find that using any single conformer fails to reproduce experimental interproton distances. We find the use of a single conformer significantly overestimates the molecular bend angle while also ignoring flexibility; in addition, we show that the average bend angle and flexibility are both linked to the relative stability of the NTB phase.

Flexural bending curvature and yield zone of subducting plates

ABSTRACT We quantify flexural deformation of subducting oceanic plates at a global array of 15 ocean trenches, using a new approach of modelling spatial variations in flexural bending shape and curvature. The investigated trenches are chosen to represent a diverse range of subducting plate age of 24–150 Ma, including the Middle America, Peru, Chile, West and East Aleutian, Sumatra, North and South Philippine, Tonga, Kermadec, Kuril, Japan, Izu-Bonin, and South and North Mariana. The studied trenches show systematic intra- and inter-trench variability in the calculated flexural bending curvature, stress distribution, extensional brittle yield zone, and effective elastic plate thickness Te of the subducting plates. We find that subducting plate age is a critical factor controlling the bending curvature and the corresponding extensional yield zone. The width, depth, and area of the extensional yield zone are all calculated to increase systematically with the subducting plate age. The newly-developed curvature analysis can yield continuously varying apparent Te(x) from the trench axis to outer rise. The calculated extensional yield zones from the curvature analysis are in general consistent with the observed normal faulting earthquakes of magnitude≥6.0 at the 15 global trenches. Our analyses also reveal that the five deepest regions of the global trenches, i.e. the Challenger, Horizon, Serena, and Scholl Deeps and Galathea Depth, are associated with relatively large flexural bending and calculated yield zones comparing to their respective adjacent trench segments. The Serena and Challenger Deeps of the S. Mariana trench are calculated to have the largest flexural bending among the five deeps.

Single Molecule Magnets: Single Molecule Magnetism with Strong Magnetic Anisotropy and Enhanced Dy∙∙∙Dy Coupling in Three Isomers of Dy‐Oxide Clusterfullerene Dy2O@C82 (Adv. Sci. 20/2019)

In article number 1901352, Fupin Liu, Stanislav M. Avdoshenko, Alexey A. Popov, Ning Chen, and co-workers synthesize a new class of single-molecule magnets (SMMs) based on fullerenes encapsulating Dy2O species. The endohedral Dy–(μ2-O)–Dy units have a bent shape with unusually short Dy–O bonds. All three isomers of Dy2O@C82 show SMM behavior with broad magnetic hysteresis. Magnetic moments of Dy ions are aligned along the Dy–O bonds and are strongly antiferromagnetically coupled.

Mechanical model of Golgi apparatus

The Golgi apparatus has intrigued researchers since its discovery and despite the advances, there are still many open questions in regards to its shape and function. We propose a mechanical model of Golgi apparatus stack and explain its most elementary geometrical properties: the equilibrium number of cisternae, the stack size, and its general equilibrium shape. Combining both analytical and numerical methods we successfully reconstruct the stack morphology within the theory of bending elasticity. We demonstrate that energy-wise the stack prefers an overall bent shape and show strong evidence that the adhesion strength determines the equilibrium number of cisternae per stack. We explore the morphological role of fenestrations and discuss their impact on the overall stack structure. We also comment on the effects of the asymmetry in the composition of membrane leaflets on the shape of the cisternae and thus offer a broad steady-state study of the stack morphology and present a method that can be used also for other membrane-bound organelles.

Laboratory Tests on Composite Beam - Accuracy of Modal Analysis Results

The primary aim of this research was to verify accuracy of results of the modal analysis on the composite beam. The research is based on the identification technique, which determines structural characteristics from the measured values of dynamic response. The method uses measured data to optimal update of the stiffness matrix to get numerical model that matched with measured data. This can be used for further calculation to determine the effect of damage to the stiffness of the beam. The experimental beam was made of wooden boards and plasterboards, which were attached to each other by a lot of screws. It was simply supported beam of total length 4m. The stiffness characteristic of beam was determined from experimental measurement of the beam deflection from a load. A total of 24 accelerometers were placed along of the beam. Accelerometers were recording vertical acceleration and the acceleration measurement record lasted for 60 seconds. We gained amplitude spectrum of acceleration from the measured acceleration values by using the fast Fourier transform (FFT). The first eigenfrequencies were determined from the amplitude spectrum. The measured value of first frequencies was f1 = 11.7Hz while the calculated value of first frequency was f1 = 11.6Hz. Other frequencies and shapes were also calculated and measured. When comparing them we need to be careful. The spacing of the transducers very well describes the vertical bending shapes while there is little information about torsional vibration shapes. We are planning extend these results by measurement with a pair of accelerometers located along the beam to verify torsional mode-shapes too. The conclusions and results of this experiment are used in calculations for system identification and determination the change in stiffness value of the damaged beam. The beam corrupted by removing the screws from the beam has changed the stiffness properties of the beam. This change is reflected as increment/decrement of original stiffness matrix - adjusted stiffness matrix.

Design, Optimization and Improvement of FBG Flexible Sensor for Slope Displacement Profiles Measurement.

The accurate measurement of slope displacement profiles using a fiber Bragg grating flexible sensor is limited due to the influence of accumulative measurement errors. The measurement errors vary with the deformation forms of the sensor, which dramatically affects the measurement accuracy of the slope displacement profiles. To tackle the limitations and improve the measurement precision of displacement profiles, a segmental correction method based on strain increments clustering was proposed. A K-means clustering algorithm was used to automatically identify the deformation segments of a flexible sensor with different bending shapes. Then, the particle swarm optimization method was adopted to determine the correction coefficients corresponding to different deformation segments. Both finite element simulations and experiments were performed to validate the superiority of the proposed method. The experimental results indicated that the mean absolute errors (MAEs) percentages of the reconstructed displacements using the proposed method for six different bending shapes were 1.87%, 5.28%, 6.98%, 7.62%, 4.16% and 8.31%, respectively, which had improved the accuracy by 26.83%, 18.94%, 29.49%, 26.35%, 7.39%, and 19.65%, respectively. Therefore, it was confirmed that the proposed correction method was competent for effectively mitigating the measurement errors and improving the measurement accuracy of slope displacement profiles, and it presented a vital significance and application promotion value.

Single Molecule Magnetism with Strong Magnetic Anisotropy and Enhanced Dy∙∙∙Dy Coupling in Three Isomers of Dy-Oxide Clusterfullerene Dy2O@C82.

A new class of single‐molecule magnets (SMMs) based on Dy‐oxide clusterfullerenes is synthesized. Three isomers of Dy2O@C82 with C s(6), C 3v(8), and C 2v(9) cage symmetries are characterized by single‐crystal X‐ray diffraction, which shows that the endohedral Dy−(µ2‐O)−Dy cluster has bent shape with very short Dy−O bonds. Dy2O@C82 isomers show SMM behavior with broad magnetic hysteresis, but the temperature and magnetization relaxation depend strongly on the fullerene cage. The short Dy−O distances and the large negative charge of the oxide ion in Dy2O@C82 result in the very strong magnetic anisotropy of Dy ions. Their magnetic moments are aligned along the Dy−O bonds and are antiferromagnetically (AFM) coupled. At low temperatures, relaxation of magnetization in Dy2O@C82 proceeds via the ferromagnetically (FM)‐coupled excited state, giving Arrhenius behavior with the effective barriers equal to the AFM‐FM energy difference. The AFM‐FM energy differences of 5.4–12.9 cm−1 in Dy2O@C82 are considerably larger than in SMMs with {Dy2O2} bridges, and the Dy∙∙∙Dy exchange coupling in Dy2O@C82 is the strongest among all dinuclear Dy SMMs with diamagnetic bridges. Dy‐oxide clusterfullerenes provide a playground for the further tuning of molecular magnetism via variation of the size and shape of the fullerene cage.

Modification of natural waterway shape as a river trash interceptor–an approach model for Citarum River recovery

The Citarum River is the most polluted river in Indonesia. The river irrigates three cascade reservoir such as Saguling, Cirata and Jatiluhur, which serve for hydroelectric power plant, drinking water, agricultural irrigation and fishery. Solid municipal waste and agricultural debris that is dumped into the river cause destruction of river habitats, flooding and shallowing especially in cascade reservoirs. This study aims to develop an idea of river recovery from waste, by using namely river trash interceptor (RTI) located at the Citarum river tributaries due to the economic consideration and efficiency. By using CFD (Computational Fluid Dynamics) and Particle Tracing module, the form of the interceptor is simulated based on the mostly general form of the Citarum River waterway; straight line shape, bend shape and U-type shape. The parameters used are river depth, river width, water discharge, particle size and density. These results of this study could be used as a reference for decision makers and developers on further development of the RTI in the near future.

Bending shape memory behaviours of carbon fibre reinforced polyurethane-type shape memory polymer composites under relatively small deformation: Characterisation and computational simulation

Shape memory polyurethanes (SMPU) have been of great interest in biomedical applications because of their unique ability to recover a primary shape by external actuation. This advantage can allow for easy suture and minimum tissue damage caused by surgery. Since SMPU suffer from low stiffness and low strength, carbon fibres have been widely used to reinforce SMPU, and their shape memory properties have been investigated using thermomechanical tensile tests. In reality, however, bending situations are more common than tensile situations, such as human skulls. In this study, carbon fibre reinforced SMPU (CF/SMPU) composites were studied as promising cranial implants that can offer shape memory properties, shape flexibility and high strength. First, the basic properties of pristine SMPU and CF/SMPU composites were characterised, including glass transition temperature (Tg), the viscosity of SMPU, the morphology of CF/SMPU, and their tensile and flexural mechanical properties. Then, a new method using rheometer was developed to study the shape memory behaviours of SMPU and CF/SMPU with three-point bending under relatively small deformations (≤1%), including flexural stress during programming and cooling, and bending recovery force during shape recovery. Finally, due to the invisibility of recovery process that was conducted in an enclosed temperature-controlling chamber of rheometer, the finite element method (FEM) was used to simulate the bending recovery test. The results showed carbon fibres significantly enhanced the mechanical properties (Young's modulus and flexural modulus) of SMPU. In terms of bending shape recovery, compared to pristine SMPU, CF/SMPU composites obtained substantially higher flexural stress during programming and cooling processes, and larger, more stable recovery force during recovery. The FEM results consolidated the peak recovery force of SMPU and the continuously growing recovery force of CF/SMPU as the temperature increased. Our findings on the improved mechanical and shape memory properties can provide a solid foundation for the potential applications of CF/SMPU composites as cranial implants.

CALCULATION OF THE FLAT BENDING SHAPE STABILITY OF RECTANGULAR CROSS SECTION BEAMS WITH REGARD TO CREEP

Objectives. The article presents the conclusion of the resolving equation for calculating the stability of the flat form of deformation of prismatic beams, taking into account the rheological properties of the material.Method. The problem is reduced to a second-order differential equation for the twist angle, which is solved numerically by the finite difference method in combination with the Euler method.Result. The obtained differential equation allows one to take into account the presence of initial imperfections in the form of the initial deflection of the beam, the initial angle of twist, and also the eccentricity of the applied load. The solution of the test problem for a cantilever polymer beam under the action of a concentrated force is presented. The non-linear Maxwell-Gurevich equation is used as the creep law. The value of the long-term critical load is introduced and it is shown that with a load less than the long-term critical creep is limited. It has been established that, as with the squeezed rods, with a load less than the long-term critical, the growth rate of the displacements with time decays. When F = F_dl, the displacements grow at a constant speed, and when F&gt; F_dl, the growth rate of displacements increases with time. The results obtained confirm the validity of the chosen method.Conclusion. A universal resolving equation is obtained for calculating the stability of a flat shape of bending of rectangular beams, suitable for arbitrary creep laws.

High-Gain MIMO Dipole Antennas With Mechanical Steerable Main Beam for 5G Small Cell

A dipole antenna with a bent dumbbell shape was positioned above and horizontal to a metal reflector to improve peak gain and steering of the radiation pattern. A parasitic square patch etched on the bottom side of the dumbbell arms provided a feeding delay line for producing dipole radiation in the 3600 MHz band. For gain enhancement and beam reconfiguration, the height of the horizontal dipole and the metal reflector could be adjusted to generate constructive reflections in phase with the radiated waves. When a dipole antenna with a height equal to half a wavelength was installed above the metal reflector, it exhibited a tilted main beam of 48° and maximum gain reached 9.2 dBi. A multiple-input–multiple-output antenna with a pair of strip stubs was also investigated. Simulation and measurement results indicated that the proposed structure achieved good isolation. The antenna had an impedance bandwidth (VSWR ≤ 2) of approximately 19.0% (3146–3818 MHz) and a low coupling ( S 21) of less than −25 dB. In this band, the average gain enhancement approximated 5.1 dBi.

Simulation Analysis of the Bed of Needling Machine Producing High Gram Weight Nonwovens

The needle punctures non-woven fabrics up and down reciprocating when the needling machine producing high gram weight nonwovens is working. The bending deformation of the supporting bed, an important part, will be caused by impact loads such as penetration force. Based on the basic principle of mechanical vibration, the vibration bending and mode shapes of the supporting were analyzed by field measurement and finite element simulation. The results showed that the deflection of the bed was affected by the penetration force under certain working conditions. But the influence value was small and the downward bending deflection was within the allowable range. The needling process would not cause resonance of the machine since its first four natural frequencies in Z direction were much larger than the working frequencies. The engineering significance of the study is to ensure that the needle punching machine meets the requirements of strength and stiffness, and realizes the function of producing high gram weight nonwovens.

One-step rapid preparation of CNTs using the spark plasma–assisted pyrolysis of melamine and its photoluminescence properties

In this study, carbon nanotubes (CNTs) were successfully fabricated using a novel spark plasma–assisted pyrolysis (SPAP) method at 700–900 °C. The existence of CNTs was confirmed in all samples, the diameter of the CNTs is approximately 40–50 nm. The CNTs fabricated at 750 °C presented a helical shape, which is different from the CNTs fabricated at other temperatures which presented a bending shape. The defects of CNTs, such as bending and abnormal layer spacing, are explained through the TEM observations. The sharp diffraction peak from the XRD result and the ID/IG ratio (a minimum of 0.772) from the Raman result revealed that the CNTs prepared at higher temperature possess better crystallinity. The photoluminescence results show that the CNTs produced exhibited strong emission peaks, and the intensity of photoluminescence could be enhanced by increasing the preparation temperature. The highlighted technique is capable of achieving the preparation of CNTs quickly, safely, and inexpensively. This technique has provided a new possibility for other materials of preparation such as boron nitride nanotubes.