Simple Bending Research Articles

Analysis of rice husk concrete samples observed by scanning electron microscopy

This paper discusses the microscopic analysis of a biobased building material. The material is rice husk concrete from the rice fields of Kovié, Togo. Our analysis is based on the results of an experiment conducted on a sample to determine its chemical composition and to observe the cohesion of the cement-rice husk mixture, which was demonstrated by subjecting a sample of the material to simple bending. We observe a constitution composed of chemical elements mainly associated with the vegetable and cementitious matter as well as zones of weakness favorable to the development of cracks, within the mixture.

Comparative study of Li-ion 21700 cylindrical cell under mechanical deformation

Lithium-ion batteries (LIBs) are an important component of the automotive industry in terms of electrification. Regarding their safety, the researchers perform different scenarios in which they follow closely and carefully their behavior under the action of induced requests. The most common mechanical abuse tests are three-point bending, simple bending, deformation with hemispherical punch head and nail penetration. In this article, the behavior of the 21700 lithium-ion cell is debated and the results are compared. First, experimental tests are performed and the results are validated with FEM model, to check the veracity of the experiment. Also, the interpreted results can be used in future researches regarding safety of batteries.

Arbitrarily and repeatedly programmable multi-layer soft actuators via “stress-caching”

Multi-layered strategy is prevalent in actuator fabrication since only a mismatch of geometric changing between layer(s) under the external stimulus is required, allowing to avoid meticulous molecular synthesis. Nonetheless, their actuation manners are usually limited to simple bending, of which the direction as well as amplitude are not (re)programmable after synthesis. Here, an arbitrarily and repeatedly programmable multi-layered actuator via “stress-caching”, where a shape memory polymer (SMP) is sandwiched with two coated hydrogel layers, is presented. Via varying the swelling/de-swelling degree between the top and bottom hydrogel layers, the designed internal stress, determining the bending direction and angle, was stored within the actuator due to the constraint of the rigid SMP layer. Upon heating, the release of the cached stress induced a “snap-like” fast actuation and the resultant geometry can be designed, preserved or recovered on demand. Additionally, the flame-retardant hydrogel layers safeguarded the actuator to work at high temperatures (even directly exposed to flame), ensuring potential applications in a fire-rescuing scenario as demonstrated. Thus, our stress-caching approach shall diversify the designs of actuator since other myriad smart materials with distinct responsiveness and functionality can be straightforwardly employed.

Elastoplastic analysis of reinforced concrete space frames using the uniaxial and biaxial bending method

The scope of the work involves reinforced concrete frame structures with variations in structural design conception for columns with biaxial bending or uniaxial bending. The beams are designed with simple bending criteria for singly or doubly reinforced beams, or uniaxial bending. The analysis and design criteria are according to NBR 6118:2014. Structure analysis in elastoplastic regimen with the incremental analysis method is performed to detect plastic hinge formation order, collapse load factor, displacements, and rotation capacity of cross sections with the criteria established in the current building codes. The study evaluates the influence of the defined concepts on the structure’s elastoplastic behavior. The biaxial and uniaxial bending method is presented as an important formulation for obtaining the collapse load factor using the elastic stiffness matrix with modifications. The algorithms presented enable the development of research without the need for expensive commercial software licenses.

Three-Dimensional Uncoupled Fluid Structure Analysis of Small Unmanned Aerial Vehicle Wing

Analyzing the interaction between a fluid and an exposed structure is vital in the design of numerous applications, including the optimization of aerodynamic bodies such as the flexible wings of small unmanned aerial vehicles. Various techniques currently exist to study such fluid/structure interactions, including experimental approaches and numerical techniques that couple fluid and structural analysis tools. In this study, a novel uncoupled static aeroelastic analysis method is demonstrated for determination of the aeroelastic response of three-dimensional wings for the first time. The results indicate that this uncoupled static aeroelastic analysis method is capable of accurately predicting the pressure and displacement fields of a flexible wing, exhibiting at most a 2% error relative to traditional coupled aeroelastic analysis results and a 2.3% error relative to experimental results. Additionally, because the fluid and structural solvers are uncoupled, it is herein demonstrated that the uncoupled static aeroelastic analysis method is capable of reusing a single computationally expensive fluid data set to evaluate multiple internal wing structural configurations across a range of angles of attack while maintaining similar levels of accuracy, thereby reducing the total computational expense by as much as 70%. Furthermore, it is also demonstrated that the uncoupled static aeroelastic analysis method is suitable for preliminary design optimization of the internal structure of wings, which may experience either simple (bending only) or complex (bending and twisting) deformation.

Material Parameters Sensitivity on Springback Modelling of Simple Bending Process

Springback is one of the major defects that continuously concerns the sheet metal experts’ community. It is has long been known that the sheet thickness, the bending angle and the yield stress of the material primarily affect the angle change after the tools’ release. Besides, the consideration of the kinematic hardening (KH) model has powerful influence on the modelling results, too. In this study, we overviewed several possible factors on the springback with finite element modeling of a simple V-die bending operation, highlighting the effect of the material variables on the final shape. AutoForm® R7 software and the built-in theory of kinematic hardening were used for the material characterization, coupled with the Hockett-Sherby isotropic hardening rule as well as the Yld89 yield criterion. The material data for modeling kinematic hardening behavior were obtained by cyclic tension-compression tests, whilst the isotropic hardening and the yield surface parameters were acquired by simple uniaxial tension tests. The simulation results were compared to the experimental springback observations obtained by a CNC bending machine, without using springback compensation. A detailed parametric study was also carried out to highlight the level of criticality of the applied material variables on the final angle change.

Stiffness estimation of planar spiral spring based on Gaussian process regression

Planar spiral spring is important for the dimensional miniaturisation of motor-based elastic actuators. However, when the stiffness calculation of the spring arm is based on simple beam bending theory, the results possess substantial errors compared with the stiffness obtained from finite-element analysis (FEA). It deems that the errors arise from the spiral length term in the calculation formula. Two Gaussian process regression models are trained to amend this term in the stiffness calculation of spring arm and complete spring. For the former, 216 spring arms’ data sets, including different spiral radiuses, pitches, wrap angles and the stiffness from FEA, are employed for training. The latter engages 180 double-arm springs’ data sets, including widths instead of wrap angles. The simulation of five spring arms and five planar spiral springs with arbitrary dimensional parameters verifies that the absolute values of errors between the predicted stiffness and the stiffness from FEA are reduced to be less than 0.5% and 2.8%, respectively. A planar spiral spring for a powered ankle–foot prosthesis is designed and manufactured to verify further, of which the predicted value possesses a 3.25% error compared with the measured stiffness. Therefore, the amendment based on the prediction of trained models is available.

Mechanical strain modulation of domain wall currents across LiNbO3 nanosensors

Recently, studies on low-dimensional conducting domain walls (DWs) in insulating ferroelectrics have opened up new research areas that allow information to be mechanically written and electrically read on the nanoscale. Large strains in thin films can change the polarization gradient across the DW region and thus increasing the DW current significantly. This phenomenon can enable the development of high sensitivity mechanical vibration sensors. In this study, the effects of variable uniaxial strain on the structures of 180° conducting DWs in LiNbO3 (LNO) single-crystal thin films bonded onto Si/SiO2 substrates were investigated. After the creation of antiparallel domains within each LNO nanosensor integrated at the film surface, strain modulation of DW currents was observed through simple mechanical bending of the film. The DW current increases under application of tensile strain along the axis of polarization, but decreases under application of in-plane compression by a factor of approximately 25. Phase field simulations showed the dramatic change in polarization gradients around the DW regions under the increase in tensile strain, which reduced the band gap. Repetitive band-gap narrowing/broadening with change in local electric field intensity under vibrating mechanical forces can periodically modulate both the carrier density and the DW conduction in the sensors. This finding not only provides the new fundamental physics to enrich the ferroelectric theory, but also paves the way to the near-future development of bending actuators, piezolighters, and micro-/nano-manipulators, etc.

Formability of roll-formed carbon fibre reinforced metal hybrid components and its experimental validation

Carbon Fibre Reinforced Metal Hybrid (CFRMH) materials that combine a sheet metal substrate with a reinforcing carbon fibre patch represent a promising solution to reduce weight while increasing the structural and crash performance of future automotive vehicles. CFRMHs cannot be formed with conventional stamping processes and at high volumes. This currently reduces their widespread application. Roll forming is increasingly used in the automobile industry for the forming of lightweight and high-strength metal structural components. The major deformation mode in roll forming is simple bending and this reduces interlaminar shear and compressive stresses that lead to fibre failure and delamination issues when stamping CFRMH sheet materials. This work analyses the potential of applying the conventional roll forming process for the manufacture of a simple top hat section shape from CFRMH sheet. For this, first, the material is produced in a hot press and then formed to shape in a laboratory roll forming facility at room temperature. Different layup sequences are tested, and component quality is analysed after roll forming by visual inspection. The results suggest that roll forming presents a promising manufacturing method for the production of automotive components from CFRMH sheets. The roll formed open shells are joined to produce crash box structure and tested in 3-point bending. The results show that depending on the fibre orientation a significant increase in weight specific strength is achieved.

Experimental analysis of high-temperature shape memory polymers for deployable structures

Shape memory polymers (SMPs) continue to capture interest in the aerospace industry due to their unique properties. In general, the focus has been on SMPs with low transformation temperatures below 100 °C. However, certain aerospace applications require shape memory polymers with higher transformation temperatures to prevent undesirable actuation upon heat exposure. Moreover, and despite significant work on characterizing mechanical and recovery properties of shape memory polymers, the literature lacks full-field characterization of recovery properties, in particular at elevated temperatures. In this work, a high-temperature thermoset epoxy SMP (Tg ≈ 130 °C), named EPON SMP, is thoroughly investigated. This study provides a comprehensive experimental analysis of the mechanical and shape memory properties of the aforementioned high-temperature epoxy SMP. In addition, this study uses a full-field characterization technique, Digital Image Correlation (DIC), to provide further insight on localization, heterogeneity, and local recovery of shape memory strains. Furthermore, the study evaluates the recovery properties of the EPON SMP at different loading conditions (i.e., bending and tensile) and proposes shape-recovery evaluation methods that can be later implemented on other SMPs. • An epoxy-based shape memory polymer with high switching temperature (Tg ≈ 130 °C) was considered in this work. • The temperature dependant mechanical properties were evaluated across a wide temperature range around Tg. • The shape recovery properties were studied under simple tensile and complex bending conditions. • The heterogeneities in the accumulated and recovery strains were evaluated using full-field deformation measurements. • A deep insight into the local accumulation of programmed, thermal, mechanical, and recovery strains is provided.

Dynamical response of a floating plate to water waves using a smoothed particle hydrodynamics algorithm for nonlinear elasticity

In this work, a newly developed Smoothed Particle Hydrodynamics (SPH) algorithm for nonlinear elasticity is combined with an incompressible SPH fluid solver to investigate the dynamics of a floating plate under impacts of regular water waves with a high steepness. Two scenarios of the plate's rigidity are investigated. The simulation results show that deformations of the stiffer plate mainly occur in a simple bending mode with small amplitudes, and the plate is almost submerged by a strong fluid flow over its surface. In the other scenario, the plate deforms more complexly with much higher deformation amplitudes but experiences a much weaker overwash. The more flexible plate is less resistant to wave motions and converts more wave energy into elastic deformations, and therefore, the overwash is less severe. A strong overflow exerts a pressure force onto the plate that alters the plate's dynamics and adds a viscous (damping) effect on the plate's elastic vibrations, especially in high-frequency modes. A rigorous examination of the numerical convergence and validation using the linear thin plate theory is also carried out. The new SPH algorithm for nonlinear elasticity shows its stability and reliability in evaluating finite and large elastic deformations. Therefore, it is promising for simulating elastic structures in fluid–structure interaction problems.

Flexural Tensile Strength Measurement and Determination for Kerbstones with Unsymmetrical Section

In this study, the determination of flexural tensile strength of concrete kerbstone is investigated. Currently, the flexural tensile strength of concrete kerbstone is determined using simple bending formula. However, due to the unsymmetrical cross-section of kerbstone, the bending take place on the section of kerbstone is not simple bending but bi-axial bending. The study shows how the flexural tensile strength for unsymmetrical sections should be determined. Additionally, flexural strength results obtained using the simple bending formula suggested by certain specifications and bi-axial bending formula used in the study were compared. As a result of the study, it was found that bi-axial bending formula gave higher values than that of the simple bending formula.

Deflection Estimation Model for Prestressed Concrete Slabs with Plastic Inserts Forming Voids.

Developed and patented more than 30 years ago, the system of slabs with plastic inserts has become very popular, and it is used all over the world today due to the significantly reduced cost of building construction. Experimental tests have shown that the behaviour of simple bending voided slab structures with plastic inserts during loading is very similar to that of solid slabs. However, their deflection and crack resistance are both slightly inferior to those of solid slabs. When using pretensioned reinforcement, the deflection and crack resistance of voided slabs exceed the above parameters for solid slabs. However, when using plastic inserts to form inner voids in slabs, their cross-section along the span becomes variable. In determining the stiffness of such slab, a problem arises in estimating the moment-of-inertia when the cross-section is variable. To estimate the influence of the voids formed by the plastic inserts on the deflection of prestressed concrete slabs, bending tests of two life-size reinforced concrete slabs were performed. The bending results obtained during the experiment were compared with the results obtained from the numerical model and analytical calculations.

STUDY OF THE MOVEMENT OF SOIL PARTICLES ON THE SURFACE OF A SCREW TILLAGE WORKING BODY

This study considers the interaction of soil particles with a screw tillage body, the working surface of which is made in the form of a deployed helicoid and substantially differs from the screw. Furthermore, the unfolded surface is characterised by manufacturability of the working body, since it is possible to calculate the geometric dimensions of a flat workpiece, which is formed into a finished product by simple bending with minimal plastic deformations. The purpose of this paper was to conduct theoretical and experimental studies of the movement of soil particles along the helical surface of the tillage working body, which is made in the form of a deployed helicoid. Mathematical modelling of the processes of movement of soil particles along the helical surface of a tillage working body was described based on general laws and principles of analytical and differential mathematics, theoretical and analytical mechanics. Experimental studies were carried out using a methodology with elements of mathematical statistics, mathematical methods of optimal planning of a multifactor experiment. The analysis of the results of experimental and theoretical studies was performed using applied computer programmes and systems. Experimental studies were conducted according to standard and independently developed methods. Results: a mathematical model of the movement of soil particles along the helical surface of the tillage body was developed, and it was established that when the angle of attack of the helical tillage working body increases, the lifting value of soil particles increases and the area of their dispersion by the helical surface increases. The value of the coefficient of friction does not substantially affect the shape of the trajectory of the soil particle. The quality of loosening the soil most depends on the angle of attack of the screw surface and the angular speed of rotation of the working body. The materials of this paper can be used by scientists for further research and practices in the selection of tillage units.

Eksplorasi Produk Aksesoris dari Bahan Limbah Botol Plastik dengan Metode Fabrikasi Sederhana

Plastic is an element that is widely used in modern human life. There are many benefits of using this plastic but it also brings harm. Plastic waste can pollute the environment, both land and sea and this is very dangerous for human survival. Therefore, efforts need to be made to reduce the amount of plastic waste, one of which is by processing plastic bottle waste into accessory products such as necklaces, bracelets, earrings, mask connectors and so on.Techniques that can be used in the exploration of plastic bottles, especially hard and soft plastic types to become accessories, are simple fabrication methods, including cutting, heating, softening, bending, and forming.. The method used in this service consists of 2 stages, namely the counseling stage by explaining the importance of processing plastic waste and showing examples that have been made and the training stage. With this method, it is hoped that the training participants will get a better picture and be able to be creative. This training activity was carried out in RT 6 RW 2 Lowokwaru Malang with the target participants being young women and housewives. One of the results of this training is a mask connector which is currently very much needed so that it can be sold and can increase skills and family income.

Addressing Surface Effects at the Particle-Continuum Interface in a Molecular Dynamics and Finite Elements Coupled Multiscale Simulation Technique.

Atomistic-to-continuum coupling methods are used to unravel molecular mechanisms of polymers and polymer composites. These multiscale techniques advantageously combine the computational efficiency of continuum approaches while keeping the accuracy of particle-based methods. The Capriccio method [Pfaller et al. Comput. Methods Appl. Mech. Eng. 2013, 260, 109-129.] is a well-proven multiscale technique, which connects finite elements (FE) with molecular dynamics (MD) in a partitioned-domain approach. A vital aspect of these multiscale methods is to provide physically sound boundary conditions to the particle domain suppressing any interface effects at the domain boundary occurring due to the coupling. These interfacial coupling artifacts still pose a significant problem, especially for amorphous polymers due to their highly irregular microstructure. We solve this problem by extending the particle-continuum interface by a layer of passive atoms which move with the outer continuum, thereby providing the missing interactions with a surrounding polymer bulk to the inner particle region. This solution allows us to successfully reproduce structural and mechanical properties obtained under conventional periodic boundary conditions, like density, stress, Young's modulus, and Poisson's ratio. Furthermore, we demonstrate the application of a nonaffine deformation by means of a simple bending test. In general, our revised method provides a framework to apply complex deformations for molecular scientists, while it allows the engineering community to examine challenging phenomena such as fracture behavior at a molecular level.

Experimental characterization and finite element validation of orthotropic 3D-printed polymeric parts

Components fabricated via Fused Filament Fabrication (FFF) have an anisotropic response, which is further complicated by an intra-part and a part-to-part variation of their mechanical properties. In addition, the mechanical characterization and analysis process has not been standardized yet, making it difficult to assess the structural behavior and verify the compliance of a part with the performance criteria in service. This paper intends to fill this gap for specific printing process parameters. First, it speculates that a linear infill with a 100% infill could help to reduce the anisotropy of the parts to a mild orthotropy. Thin components have provided a quick and preliminary confirmation of the approach. After an initial test setup design, which was required to standardize the method, the in-plane behavior was studied. Classical dog-bone specimens returned unsatisfactory results when coupled with the internal structures. As a result, the paper takes inspiration from the test methods for Uni-Directional Composites (UDCs). It uses sets of Design of Experiments (DoEs) to determine the optimal shape of the tabs. This method managed to quantify the factors of the 3 × 3 reduced elastic coefficients matrix. Finally, the paper presents a set of three-point bending, simple bending, and bending–torsion tests on samples featuring different laminations. 2D FE models tuned with the experimental properties simulated them, following the Classical Lamination Theory (CLT) approach. For consistency, a shear penalization was introduced for the out-of-plane shear. The FE models delivered an excellent mechanical response prediction; this result appears to validate the approach and the method and endorses 2D FEM and CLT as reliable tools to analyze linear infill FFF parts.

STUDY OF THE RESISTANCE TO RUPTUREAND DEFORMATION OF A BENT BEAM MADE OF OIL PALM KERNEL SHELL (OPKS) CONCRETE REINFORCED WITH BORASSUS AETHIOPUM MART (RONIER)

The present study is related to the simple bending performance of a structural element made of Oil Palm Kernel Shell Concrete (OPKSC) reinforced with Borassus Aethiopum Mart (ronier). An experimental program with the use of three (03) distinct approaches of formulation was developed. These are respectively the formulation approaches proposed by Gibigaye et al (Gibigaye et al., 2017) and Yasmine et al (Traore et al., 2015) for OPKSC and the one proposed by DreuxGorisse for conventional aggregate concretes that served as control concrete. Reinforced roast concrete beams of size 150 mm × 150 mm × 910 mm were developed in accordance with NF EN 12390-1 and subjected to four (04) point bending until failure. It was observed an improvement of the bending strength of the OPKSC compared to the conventional aggregate concrete with a rate ranging from 3 to 80% depending on the type of formulation used. Similarly, the use of plasticizers improves the bending strength of OPKSC by more than 75%. Moreover, we notice the appearance of the first cracks as soon as the applied load reaches 60% of the breaking strength in bending which emphasizes the ductile behavior of OPKSC reinforced with roast. The OPKSC reinforced with ronier is a material suitable for use in the bent elements of the structure of lightly loaded buildings.

Experimental research on a novel spring-shaped fiber-optic displacement sensor for settlement monitoring

In this paper an innovative spring-shaped fiber-optic displacement sensor (SSFODS) based on optical time domain reflectometer (OTDR) technology with simple construction and cheap cost was proposed for subgrade settlement monitoring. The sensor incorporated a simple spring-shaped fiber bending modulation that increased its sensitivity in bending, light source and detector. The sensing principle between the measured external displacement and bending loss of optical fiber was theoretically explained and its expression was also derived. Sensor calibration was conducted, which showed that the SSFODS was characterized by a large measurement range of 90 mm, minimum displacement resolution of 0.173 mm, maximum hysteresis error of 2.81% and maximum repeatability error of 8.42%, respectively. A soil drainage model test with the SSFODS was performed to study its performance in determining compression deformation of the soil. At last, a simple field monitoring application with two SSFODSs connected in series was conducted and the progressive compaction behavior of the fill slope was accurately captured by two SSFODSs. Additionally, it is possible to connect these SSFODSs in series on one optical link to realize quasi-distributed sensing monitoring. This capability supports a promising application of the sensor in geotechnical engineering for real-time monitoring of the stability of fill slopes, foundation pits and so on.

Failure analysis of a composite riser pipe under operational and spooling loads

Fibre-reinforced plastic riser pipes are on the cusp of deployment in deep waters where high specific strengths and moduli and corrosion resistance are highly advantageous. In this work, failure analysis is performed for thermoplastic composite pipe (TCP) under loads illustrative of deepwater riser operation by finite element modelling. Temperature-dependent material properties are considered. Different laminate stacking sequences are analysed and a multi-angle stack is shown to be effective for both small and large tension operating scenarios. The bending of TCP at reduced and elevated temperatures, representative of spooling in different environments, is also investigated. Temperature change causes deviation from the symmetry expected between stresses at tensile (top) and compressive (bottom) sides of the pipe under simple bending. It is shown that TCP can be optimised for spooling by orientating unidirectional layers at an ‘intermediate’ angle that promotes utilisation of in-plane shear strength, rather than fibre or transverse strengths. Since optimising the stacking sequence for operation and spooling are effectively mutually exclusive, large spools will inevitably be required for TCP designed to operate in extreme in-service conditions.