Bending Characteristics Research Articles

Investigations on Bending Characteristics of Soft Mesh Structure using Shape Memory Alloy Spring Towards Bio-Inspired Robotic Applications

A biomimetic soft worm robot has been developed using soft mesh structured polyethylene terephthalate thermoplastic driven by shape memory alloy springs. The bending behaviour of the robot for achieving steering in peristaltic and bending for two anchor locomotion has been investigated in detail. A flex sensor is attached with the soft worm to measure the bending/steering angle. An open-loop control approach is adopted for the study of soft worm’s bending actions. In peristaltic crawling, a bending angle of 57°, 48° and 48° was achieved in upward, left and right directions, respectively. The movement of the soft worm robot has been probed towards imitating the bending action of two anchor crawling locomotion with kapton polyamide legs. In two anchor crawling, a bending angle of 60° is achieved in downward direction.

Bending characteristics of all-composite hexagon honeycomb sandwich beams: experimental tests and a three-dimensional failure mechanism map

The bending characteristics of all-composite honeycomb sandwich beams were investigated by a three-dimensional failure mechanism map and verified by three-point bending tests. In this paper, analytical models were used to predict the three-point bending stiffness, failure load and failure modes of all-composite hexagon honeycomb sandwich beams. A three-dimensional failure mechanism map was generated to characterize the dominant failure mechanism based upon failure load criteria for shear buckling, shear fracture, debonding, intracellular dimpling and face fracture. The tailor-folding method was used to fabricate the all-composite honeycomb sandwich beams. To verify the analytical models and three-dimensional failure mechanism map, three-point bending tests were carried out on the sandwich beams with different core relative densities, face thicknesses and loading spans. It was observed that the analytical predictions were in good agreement with the experimental results. A single case with the supreme load-weight ratio on the failure mechanism map has been identified and verified. Besides, the paths of maximum load design for a series of geometrical parameters were also traced. The study provides insights into the role of the physical dimension in tuning the flexural property of the sandwich structure and expands the application envelope of the failure mechanism map by effectively increasing the structural analytical dimensionality.

Effect of heat treatment conditions on mechanical properties and springback of 6061 Aluminum alloy sheets

The mechanical properties and bending deformation behaviors of homogenization treated (HT), solution treated (ST), natural aging (NA) treated and T6 6061 aluminum alloy sheets were investigated by tensile tests and three-point bending tests, respectively. The results showed that the heat treatment conditions have a significant impact on mechanical properties and bending characteristic. Bending radius and thickness of the HT alloy is the highest, and its springback angle is the lowest. However, the deformation mechanism of T6-8h alloy is just the opposite. The bending characteristics are attributed to the combined effects of yield strength, strain-hardening exponent and coefficient of the neutral layer. The simulation results are in good agreement with the experiment.

Mechanical Stability of Rayon Fibre Reinforced Concrete

The article analyses the mechanical stability of concrete with additions of rayon fibre by determining the fresh property like workability and strength properties like compressive strength, split tensile strength and flexural strength of concrete of grade M30.The effect of rayon fibre on reinforced concrete in variations of 0%, 0.1%, 0.15% and 0.2% was studied. This work includes the casting and testing of rayon fibre reinforced concrete. The test was conducted after 7 days and 28 days and the results were compared with conventional concrete.The mix design of strength of 30 N/mm2 was implemented using Indian Standard method.Concrete is extensively used in the construction industry. Traditional concrete is incapable of taking higher tensile stress and hence fails upon tensile stress. The Rayon fibre induced concrete is an excellent substitute for this problem. This paper reports on the results of an experimental investigation for assessing the behavior of rayon fibre in reinforced concrete and alsoto study the properties of materials and procedure of mix design of fiber reinforced concrete. The main motive is to determine the properties of concrete by adding rayon fibre to the concrete in certain percentage and comparing it with the traditional concreteand physical characteristics of rayon fibres. Rayon fibre is a manufactured fibre made out of natural sources such as wood, agricultural products that are regenerated and cellulose fibre, which can be used to enhance the bending characteristics of concrete.Micro fibres like rayon provide flexibility and also act as reinforcement. Rayon fibre reinforced concrete can be used in the construction of mega structures.

STATIC BENDING OF TWO-DIRECTIONAL FUNCTIONALLY GRADED SANDWICH PLATES USING A THIRD-ORDER SHEAR DEFORMATION FINITE ELEMENT MODEL

In this paper, static bending of two-direction functionally graded sandwich (2D-FGSW) plates is studied by using a finite element model. The plates consist of a homogeneous core and two functionally graded skin layers with material properties being graded in both the thickness and length directions by power gradation laws. Based on a third-order shear deformation theory, a finite element model is derived and employed in the analysis. Bending characteristics, including deflections and stresses are evaluated for the plates with classical boundary conditions under various types of distributed load. The effects of material distribution and layer thickness ratio on the static bending behavior of the plates are examined and highlighted.

STATIC BENDING OF TWO-DIRECTIONAL FUNCTIONALLY GRADED SANDWICH PLATES USING A THIRD-ORDER SHEAR DEFORMATION FINITE ELEMENT MODEL

In this paper, static bending of two-direction functionally graded sandwich (2D-FGSW) plates is studied by using a finite element model. The plates consist of a homogeneous core and two functionally graded skin layers with material properties being graded in both the thickness and length directions by power gradation laws. Based on a third-order shear deformation theory, a finite element model is derived and employed in the analysis. Bending characteristics, including deflections and stresses are evaluated for the plates with classical boundary conditions under various types of distributed load. The effects of material distribution and layer thickness ratio on the static bending behavior of the plates are examined and highlighted.

Analysis of misalignment, twist, and bend in few-mode fibers using spatially and spectrally resolved imaging

Abstract Modal pattern and power in few-mode fibers, with dominant high-order modes by mode excitation at different core offset misalignments, were simulated and experimentally examined using the spatially and spectrally resolved imaging (S2) technique. The far-field specklegram of the interference between the LP11 and LP21 modes was observed. Twisting and bending characteristics of the LP11 mode in a two-mode fiber (TMF) were presented by reconstructing the LP11 mode using the S2 imaging technique. The experimental results showed that the LP11 mode specklegram rotated 76.4% of the fiber twist angle and 0.58 deg/m−1 of the fiber curvature in the TMF. The relative peak amplitude was measured to decrease the fiber twist angle by 0.009 dB/deg and the curvature by 0.056 dB/m−1. These characteristics allow for future use of the LP11 mode in fiber specklegram sensors. Additionally, the advantage of the S2 method for specklegram sensors is that it does not require the excitation of only the LP11 mode in the fiber, which simplifies the experiment.

Development of Visible Manipulator With Multi-Gear Array Mechanism for Laparoscopic Surgery

In recent years, robotic technology has been introduced to medical fields, and many surgical robots have been proposed for minimally invasive surgery (MIS). However, due to the limitations in dexterity imposed by surgical instruments and occlusion area, surgeons experience great difficulties during operations. In this paper, we propose a visible manipulator for laparoscopic surgery. Unlike other multiple degree-of-freedom (DOF) manipulators that utilize compliant parts or tendons and pulleys, our proposed manipulator adopts a multi-gear array mechanism to perform the yaw and pitch motions. The manipulator is integrated with a visualization unit to provide macroscopic images for observation in a constrained cavity. Moreover, flexible surgical tools with different functions can be inserted through the central channel of the manipulator to perform diagnostic or therapeutic procedures. A master-slave system is developed to control the bending motions. Bending characteristics experiments and load capacity experiments are performed. The experimental results demonstrate that the proposed manipulator can perform bending motions with a yaw angle range of −76.8°∼76.2° and a pitch angle range of −75.2°∼75.6°. The manipulator can lift a workload of 250 g during yaw motion and a workload of 150 g during pitch motion, demonstrating the potential clinical value of the visible manipulator for robot-assisted surgery.

Experimental Study on Dry and Wet Bending Behavior of CF/GF Inter Laminated Hybrid Composites

Experimental study on the bending characteristics of dry and wet state (100 °C boiled for 2 hours) in the same layering method, carbon (T700 unidirectional cloth)/glass (EWR800 multiaxial cloth) interlaminar hybrid composites with different mixing ratios. At the same time, the effects of 430LV vinyl resin and QC-350 epoxy resin on the bending properties of hybrid composites were compared and analyzed. The test results show that, In the same mixing ratio and the same test condition, QC-350 epoxy resin corresponding to the hybrid sample bending performance is better than 430LV vinyl resin; the wet bending strength and modulus of hybrid bending specimens are lower than those of dry bending specimens in varying degrees. The flexural strength and modulus of hybrid specimens increase with the increase of carbon fiber volume fraction. And as the volume of carbon fiber in the sample increases, the flexural strength and modulus of the hybrid sample increase to varying degrees. In addition, the results also show that the bending strength and modulus of hybrid bending specimens without post-curing treatment decrease in varying degrees at the same mixing ratio, whether in dry or wet state.

Effect of Combination Twisting With Bending Characteristics on Critical Current of Quasi-Isotropic HTS Strand

Effect of Combination Twisting With Bending Characteristics on Critical Current of Quasi-Isotropic HTS Strand

The isotropic organization of DEM structure and extraction of valley lines using hexagonal grid

AbstractThe automatic extraction of valley lines (VLs) from digital elevation models (DEMs) has had a long history in the GIS and hydrology fields. The quality of the extracted results relies on the geometrical shape, spatial tessellation, and placement of the grids in the DEM structure. The traditional DEM structure consists of square grids with an eight‐neighborhood relationship, where there is an inconsistent distance measurement between orthogonal neighborhoods and diagonal neighborhoods. The directional difference results in the extracted VLs by the D8 algorithm not guaranteeing isotropy characteristics. Alternatively, hexagonal grids have been proved to be advantageous over square grids due to their consistent connectivity, isotropy of local neighborhoods, higher symmetry, increased compactness, and more. Considering the merits above, this study develops an approach to VL extraction from DEMs based on hexagonal grids. First, the pre‐process phase contains the depression filling, flow direction calculation, and flow accumulation calculation based on the six‐neighborhood relationship. Then, the flow arcs are connected, followed by estimating the flow direction. Finally, the connected paths are organized into a tree structure. To explore the effectiveness of hexagonal grids, comparative experiments are implemented against traditional DEMs with square grids using three sample regions. By analyzing the results between these two grid structures via visual and quantitative comparison, we conclude that the hexagonal grid structure has an outstanding ability in maintaining the location accuracy and bending characteristics of extracted valley networks. That is to say, the DEM‐derived VLs based on hexagonal grids have better spatial agreement with mapped river systems and lower shape diversion under the same resolution representation. Therefore, the DEMs with hexagonal grids can extract finer valley networks with the same data volume relative to traditional DEM.

Finite element modelling of large radius bending operation

The finite element method is the default choice for the prediction of complex forming processes. In this work, this method is applied to the prediction of large radius air bending of high-strength steels. Three distinct formulations are used for the prediction: plane, shell and solid. Appropriate mesh parameters and material implementation are used in order to obtain high prediction accuracy and to minimise the calculation time. A new law for the approximation of the hardening behaviour of high-strength steels is introduced and further used for the minimisation of the prediction error. Contact points position, springback, bending force and bend allowance are used for the comparison between experimental and simulation data. Obtained results show that the plane model is not a suitable option for the modelling of large radius air bending, due to an instable behaviour with respect to the number of elements through the thickness. Shell and solid formulations, however, provide high accuracy prediction for the considered bending characteristics with comparable predictive quality. [Submitted 21 August 2018; Accepted 27 January 2019]

Experimental Research on the Bending Characteristics of Glycyrrhiza glabra Stems

HighlightsA quadratic orthogonal rotation combination design was used to test the influences of four factors.The significant influence of each factor was obtained using the analysis of variance method.Interactions of the factors were analyzed using the response surface method.Abstract. To provide a theoretical basis for the design of harvesting and processing machinery for Glycyrrhiza glabra stems and for energy conservation during processing, the bending characteristics of G. glabra stems were studied. The comprehensive influences of four factors (loading position diameter, loading speed, span, and moisture content) on the bending characteristics of G. glabra stems were tested using a quadratic orthogonal rotation combination design. The results indicated that the single factors loading position diameter and span had a significant influence on the bending characteristics of G. glabra stems. In addition, as the loading position diameter increased, the maximum bending force and bending energy of G. glabra stems tended to increase, while the bending stress tended to decrease. As the span increased, the maximum bending force and bending energy of G. glabra stems tended to decrease, while the bending stress tended to increase. As the moisture content increased, the maximum bending force and bending stress of G. glabra stems tended to decrease, while the influence on bending energy was not significant. The loading speed had no influence on the bending characteristics of G. glabra stems. The interaction between loading position diameter and span had a significant influence on the maximum bending force and bending energy, and the interactions between loading position diameter and moisture content and between loading speed and span had a significant influence on the maximum bending stress. This study on the bending characteristics of G. glabra stems can provide a theoretical basis for the design of harvesting and processing equipment and for the pretreatment of G. glabra stems. Keywords: Bending characteristics, Licorice, Loading position, Loading speed, Moisture content, Span.

Finite element modeling of large radius bending operation

The finite element method is the default choice for the prediction of complex forming processes. In this work, this method is applied to the prediction of large radius air bending of high-strength steels. Three distinct formulations are used for the prediction: plane, shell and solid. Appropriate mesh parameters and material implementation are used in order to obtain high prediction accuracy and to minimise the calculation time. A new law for the approximation of the hardening behaviour of high-strength steels is introduced and further used for the minimisation of the prediction error. Contact points position, springback, bending force and bend allowance are used for the comparison between experimental and simulation data. Obtained results show that the plane model is not a suitable option for the modelling of large radius air bending, due to an instable behaviour with respect to the number of elements through the thickness. Shell and solid formulations, however, provide high accuracy prediction for the considered bending characteristics with comparable predictive quality. [Submitted 21 August 2018; Accepted 27 January 2019]

Springback Characteristics of Cylindrical Bending of Tailor Rolled Blanks

As a new type of variable thickness sheet structure, the TRB (tailor rolled blank) has good prospects for the development of lightweight materials in the automotive industry. However, springback is a key issue in production. Research on TRB springback characteristics has great significance for further applications due to variations in the sheet thickness and gradient distribution of the material mechanical properties. In this study, the springback characteristics of TRBs were investigated by means of the finite element code ABAQUS/USDFLD and experiments taking cylindrical bending as an example. The results showed that the cylindrical bending process of the TRB gradually evolved from three‐point bending to four‐point bending and, finally, to multipoint bending. At same time, the gradient of the thickness leads to the nonuniform longitudinal distribution of the von Mises stress. On the contrary, larger bending angles can be achieved by reducing R and improving Rd, but t/T has little effect on the bending angles. In terms of the influence of springback, increasing Rd and reducing R and t/T can lead to a smaller springback angle. This project provided an important opportunity to advance the understanding of TRB springback characteristics.

Effect of fiberglass form on the tensile and bending characteristic of epoxy composite material

This search focuses on the tensile and bending characteristics of a composite material that reinforced by various forms of fiberglass. Two fiber forms are considered; the first is bi-directional of (0°–90°) fiber direction, the second is random. The fiber thickness of bi-directional form has been investigated by considering thick and thin mats. The composite has been developed by hand lay-up process with a fiber weight ratio of 10%. Three samples of the developed composited have been compared with a base case sample (pure matrix of epoxy resin). Also, a microscopic vision has been captured on the fracture zone of tensile specimens. The results reveal that the random-form composite had maximum tensile strength and transverse stiffness, also, the thin-fiber composite showed maximum ductility.

Estimation of bending characteristics of creased paperboard using 45° tapered groove against unbalanced punch indentation

Estimation of bending characteristics of creased paperboard using 45° tapered groove against unbalanced punch indentation

Effect of profile and reinforcing the surface layers on bending behavior of 3D multi-cell spacer weft-knitted composites

3D multi-cell spacer-knitted reinforced composites are composed of knitted layers which are joined together by multiple fabric connecting layers. Despite numerous capabilities, they demonstrate inferior bending performance due to their highly looped construction as well as low fiber volume fraction. Bending characteristics could be enhanced by inserting the warp and weft yarns through the fabric’s surface layers in wale and course directions. This research aims to investigate the role of reinforcing warp and weft yarns and structure profile on bending behavior of the composites produced from 3D multi-cell spacer-knitted fabrics. 3D multi-cell spacer-knitted fabrics were produced with rectangular cross-sectional shape in single- and double-decker profiles on a computerized flat-knitting machine. The surface layers of both 3D multi-cell spacer-knitted fabrics were reinforced by glass straight yarns in course and wale directions. The produced fabrics were used to fabricate thermoset 3D composites using epoxy resin via vacuum-assisted resin-transfer method. Composite samples were subjected to three-point bending load. Statistical analysis revealed that the composite profile and presence of the reinforcing warp and weft yarns affect significantly the flexural properties of 3D-knitted composites. Accordingly, introduction of the reinforcing straight yarns causes an increase in maximum bending force by 75 and 62.5% for single and double-decker structures, respectively. In order to understand how the tensile and compressive stresses are distributed on the 3D-knitted composite structure as well as to predict their mechanical behavior, a macro-mechanical model was created in the ABAQUS software.

Parametric study of three-dimensional bending and frequency of FG-GPLRC porous circular and annular plates on different boundary conditions

Due to important role of composite materials in broad spectrum of applications, this article focused on bending and frequency characteristics of a functionally graded graphene platelet (GPL) reinforced composite (FG-GPLRC) porous circular/annular plates with various boundary conditions by employing state-space differential quadrature method (DQM). The material properties of piece-wise graphene-reinforced composites are assumed to be graded in the thickness direction of a circular/annular plates and are estimated through the modified Halpin-Tsai micromechanics model. Equations of motion are established within the framework of theory of elasticity and are formulated along the thickness direction in the form of state-space. Applying DQM along the radial direction provides a semi-analytical solution to bending and free vibration of the plate. The results of applying present approach are validated by comparing them with those reported in the literature. A thorough parametric investigation is conducted on the effects of different GPLs distributions integrated with various distribution patterns of internal porosity, thickness to radius ratio, outer to inner radius ratio, GPLs weight fraction, porosity coefficient and edge boundary conditions on the bending and frequency behavior of FG-GPLRC circular/annular plates. The results reveal a very useful practical designing hint that locating more GPLs in the vicinity of the upper and bottom surfaces of the circular/annular plates with lower outer radius to thickness ratio leads to the highest natural frequencies beside the lowest deflections in comparison with other configurations. This study could be beneficial for engineers designing and analyzing composite structures as the mainstay of high-performance devices.

Utilization of agricultural rests: Straw-based composite panels made from enzymatic modified wheat and rapeseed straw

The paper deals with the possibility of using post-harvest crop residues, namely winter wheat straw and winter rapeseed straw for the purpose of producing particleboards. In order to increase particle surface energy, particles were treated with enzymes prior to application of the adhesive; xylanases, pectinase, and a combination of both. The effect of the enzymatic treatment on the properties of the treated particles was monitored and, after the production of the boards, the influence of particle treatment on the mechanical and physical properties of the composites was also monitored. The effect of enzymatic modification on the properties of wheat and rapeseed particles was observed. The enzymes used influenced the particle surface morphology, their surface energy and equilibrium moisture content. Only the combination of pectinase and xylanase (Texazym SER 7) increased the surface energy of wheat surface from 26 mN/m (untreated) to 30 mN/m. The greatest erosion of the surface was achieved by the combination of xylanases and pectinases. After enzymatic treatment both wheat and rapeseed straw exhibited higher equilibrium moisture content. The increase of moisture of wheat straw was from 11.9 %–13.2 % and of rapeseed straw from 12.4 %–13.44 %. Although the selected enzymes had an effect on the properties of the particles, the effect of the enzymatic treatment on the equilibrium moisture, the internal bond strength and the bending characteristics of the produced particleboards were not observed. Produced boards reached low mechanical properties, internal bond strength reached values form to 61–99 mN/mm2.