Experimental,Numerical,and Analytical Studies on the Bending of Mechanically Lined Pipe

Mechanically lined pipe(MLP)is often used for offshore oil and gas transport because of its low cost and corrosion resistance.During installation and operation,the pipe may undergo severe bending deformation,which causes the liner to separate from the outer pipe and buckles,affecting the stability of the whole line.In this paper,the buckling response of MLP subjected to bending is investigated to clarify its bending characteristics by employing both experiments,numerical simulation,as theoretical methods.Two types of MLPs were manufactured with GB 45 carbon steel(SLP)and Al 6061(ALP)used as the outer pipe material,respectively.The hydraulic expansion and bending experiments of small-scale MLPs are conducted.In addition to the ovalized shape of the cross-section for the SLP specimens,the copper liner was found to wrinkle on the compressive side.In contrast,the liner of ALP remains intact without developing any wrinkling and collapse mode.In addition,a dedicated numerical framework and theoretical models were also established.It was found both the manufacturing and bending responses of the MLP can be well reproduced,and the predicted maximum moment and critical curvatures are in good agreement with the experimental results.

Effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on tensile and bending properties of high-Al-containing Mg alloys

This study investigates the effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on the uniaxial tensile and three-point bending properties of extruded Mg alloys containing high Al contents.The extruded Mg–9Al–1Zn–0.3Mn(AZ91)alloy contains lamellar-structured Mg_(17)Al_(12)discontinuous precipitates along the grain boundaries,which are formed via static precipitation during natural air cooling.The extruded Mg–11Al–1Zn–0.3Mn(AZ111)alloy contains spherical Mg_(17)Al_(12)precipitates at the grain boundaries and inside the grains,which are formed via dynamic precipitation during extrusion.Due to inhomogeneous distribution of precipitates,the AZ111 alloy consists of two different precipitate regions:precipitate-rich region with numerous precipitates and finer grains and precipitate-scarce region with a few precipitates and coarser grains.The AZ111 alloy exhibits a higher tensile strength than the AZ91 alloy because its smaller grain size and more abundant precipitates result in stronger grain-boundary hardening and precipitation hardening effects,respectively.However,the tensile elongation of the AZ111 alloy is lower than that of the AZ91 alloy because the weak cohesion between the dynamic precipitates and the matrix facilitates the crack initiation and propagation.During bending,a macrocrack initiates on the outer surface of bending specimen in both alloys.The AZ111 alloy exhibits higher bending yield strength and lower failure bending strain than the AZ91 alloy.The bending specimens of the AZ91 alloy have similar bending formability,whereas those of the AZ111 alloy exhibit considerable differences in bending formability and crack propagation behavior,depending on the distribution and number density of precipitates in the specimen.In bending specimens of the AZ111 alloy,it is found that the failure bending strain(ε_(f,bending))is inversely proportional to the area fraction of precipitates in the outer zone of bending specimen(A_(ppt)),with a relationship ofε_(f,bending)=–0.1A_(ppt)+5.86.

A Light and Simplified Branch Bending Method for Young Pear Trees

Aiming at high cost and low efficiency of conventional branch bending method in the modern intensive planting and labor-saving cultivation mode of young pear trees,this paper provides a new branch bending method with wide source of raw materials,cheap price and simple operation,which is also suitable for the management of low-age branches in the process of high grafting and upgrading of traditional big trees.

The Effects of the Longitudinal Axis of Loading upon Bending, Shear and Torsion of a Thin-Walled Cantilever Channel Beam

Three aluminium channel sections of US standard extruded dimension are mounted as cantilevers with x-axis symmetry. The flexural bending and shear that arise with applied axial torsion are each considered theoretically and numerically in terms of two longitudinal axes of loading not coincident with the shear centre. In particular, the warping displacements, stiffness and stress distributions are calculated for torsion applied to longitudinal axes passing through the section’s centroid and its web centre. The stress conversions derived from each action are superimposed to reveal a net sectional stress distribution. Therein, the influence of the axis position upon the net axial and shear stress distributions is established compared to previous results for each beam when loading is referred to a flexural axis through the shear centre. Within the net stress analysis is, it is shown how the constraint to free warping presented by the end fixing modifies the axial stress. The latter can be identified with the action of a ‘bimoment’ upon each thin-walled section.

Electro-chemo-mechanical analysis of the effect of bending deformation on the interface of flexible solid-state battery

Flexible solid-state battery has several unique characteristics including high flexibility,easy portability,and high safety,which may have broad application prospects in new technology products such as rollup displays,power implantable medical devices,and wearable equipments.The interfacial mechanical and electrochemical problems caused by bending deformation,resulting in the battery damage and failure,are particularly interesting.Herein,a fully coupled electro-chemo-mechanical model is developed based on the actual solid-state battery structure.Concentration-dependent material parameters,stress-dependent diffusion,and potential shift are considered.According to four bending forms(k=8/mm,0/mm,-8/mm,and free),the results show that the negative curvature bending is beneficial to reducing the plastic strain during charging/discharging,while the positive curvature is detrimental.However,with respect to the electrochemical performance,the negative curvature bending creates a negative potential shift,which causes the battery to reach the cut-off voltage earlier and results in capacity loss.These results enlighten us that suitable electrode materials and charging strategy can be tailored to reduce plastic deformation and improve battery capacity for different forms of battery bending.

A review on evaluation of crack resistance of asphalt mixture by semi-circular bending test

Although there are many kinds of fracture tests to choose from in evaluating the crack resistance of asphalt mixture,the semi-circular bending(SCB)test has attracted a lot of attention in the academic road engineering community because of its simplicity,stability,and flexibility in testing and evaluation.The SCB test has become a common method to study the cracking resistance of asphalt mixture in recent years.This paper mainly summarizes the overview of the SCB test,summarizes some research results and common characterization parameters of the SCB test method in monotone test and fatigue test in recent years,and predicts and suggests the research direction of the SCB test in the future.It is found that the research on the monotonic SCB test is more comprehensive,and the research on the SCB fatigue test needs to be further improved in the aspects of loading mode,characterization parameter selection,and so on.Researchers can flexibly adjust the geometric dimensions and the test parameters of semi-cylindrical specimens,and conduct comprehensive analysis combined with the results of numerical simulation.The crack resistance of asphalt mixture can be comprehensively evaluated by fracture energy,fracture toughness,stiffness,flexibility index and other fracture indicators,combined with the crack propagation of the specimen.The analysis of numerical simulation can confirm the test results.In order to standardize the setting of fatigue parameters for future application,it is necessary to standardize the setting of bending performance.

Numerical analysis of bending property of bi-modulus materials and a new method for measurement of tensile elastic modulus

In nature,there are widely distributed bi-modulus materials with different deformation characteristics under compressive and tensile stress states,such as concrete,rock and ceramics.Due to the lack of constitutive model that could reasonably consider the bi-modulus property of materials,and the lack of simple and reliable measurement methods for the tensile elastic parameters of materials,scientists and engineers always neglect the effect of the bi-modulus property of materials in engineering design and numerical simulation.To solve this problem,this study utilizes the uncoupled strain-driven constitutive model proposed by Latorre and Montáns(2020)to systematically study the distributions and magnitudes of stresses and strains of bi-modulus materials in the three-point bending test through the numerical method.Furthermore,a new method to synchronously measure the tensile and compressive elastic moduli of materials through the four-point bending test is proposed.The numerical results show that the bi-modulus property of materials has a significant effect on the stress,strain and displacement in the specimen utilized in the three-point and four-point bending tests.Meanwhile,the results from the numerical tests,in which the elastic constitutive model proposed by Latorre and Montáns(2020)is utilized,also indicate that the newly proposed measurement method has a good reliability.Although the new measurement method proposed in this study can synchronously and effectively measure the tensile and compressive elastic moduli,it cannot measure the tensile and compressive Poisson’s ratios.

Transient swelling-induced finite bending of hydrogel-based bilayers:analytical and FEM approaches

Hydrogels with their time-dependent intrinsic behaviors have recently been used widely in soft structures as sensors/actuators.One of the most interesting structures is the bilayer made up of hydrogels which may undergo swelling-induced bending.In this work,by proposing a semi-analytical method,the transient bending of hydrogel-based bilayers is investigated.Utilizing nonlinear solid mechanics,a robust semi-analytical solution is developed which captures the transient finite bending of hydrogel-based bilayers.Moreover,the multiphysics model of the hydrogels is implemented in the finite element method(FEM) framework to verify the developed semi-analytical procedure results.The effects of different material properties are investigated to illustrate the nonlinear behavior of these structures.The von-Mises stress contour extracted from FEM shows that the critical area of these soft structures is at the interface of the layers which experiences the maximum stress,and this area is most likely to rupture in large deformations.

Multiresolution method for bending of plates with complex shapes

A high-accuracy multiresolution method is proposed to solve mechanics problems subject to complex shapes or irregular domains.To realize this method,we design a new wavelet basis function,by which we construct a fifth-order numerical scheme for the approximation of multi-dimensional functions and their multiple integrals defined in complex domains.In the solution of differential equations,various derivatives of the unknown function are denoted as new functions.Then,the integral relations between these functions are applied in terms of wavelet approximation of multiple integrals.Therefore,the original equation with derivatives of various orders can be converted to a system of algebraic equations with discrete nodal values of the highest-order derivative.During the application of the proposed method,boundary conditions can be automatically included in the integration operations,and relevant matrices can be assured to exhibit perfect sparse patterns.As examples,we consider several second-order mathematics problems defined on regular and irregular domains and the fourth-order bending problems of plates with various shapes.By comparing the solutions obtained by the proposed method with the exact solutions,the new multiresolution method is found to have a convergence rate of fifth order.The solution accuracy of this method with only a few hundreds of nodes can be much higher than that of the finite element method(FEM)with tens of thousands of elements.In addition,because the accuracy order for direct approximation of a function using the proposed basis function is also fifth order,we may conclude that the accuracy of the proposed method is almost independent of the equation order and domain complexity.

Bending Resistance Covalent Organic Framework Superlattice:“Nano‑Hourglass”‑Induced Charge Accumulation for Flexible In‑Plane Micro‑Supercapacitors

Covalent organic framework(COF)film with highly exposed active sites is considered as the promising flexible selfsupported electrode for in-plane microsupercapacitor(MSC).Superlattice configuration assembled alternately by different nanofilms based on van der Waals force can integrate the advantages of each isolated layer to exhibit unexpected performances as MSC film electrodes,which may be a novel option to ensure energy output.Herein,a mesoporous free-standing A-COF nanofilm(pore size is 3.9 nm,averaged thickness is 4.1 nm)with imine bond linkage and a microporous B-COF nanofilm(pore size is 1.5 nm,averaged thickness is 9.3 nm)withβ-keto-enamine-linkages are prepared,and for the first time,we assembly the two lattice matching films into sandwich-type superlattices via layer-by-layer transfer,in which ABA–COF superlattice stacking into a“nano-hourglass”steric configuration that can accelerate the dynamic charge transportation/accumulation and promote the sufficient redox reactions to energy storage.The fabricated flexible MSC–ABA–COF exhibits the highest intrinsic CV of 927.9 F cm^(−3) at 10 mV s^(−1) than reported two-dimensional alloy,graphite-like carbon and undoped COF-based MSC devices so far,and shows a bending-resistant energy density of 63.2 mWh cm^(−3) even after high-angle and repeat arbitrary bending from 0 to 180°.This work provides a feasible way to meet the demand for future miniaturization and wearable electronics.

Effects of surface roughness on bending properties of rolled AZ31 alloy

This study investigated the effects of mechanical-polishing-induced surface roughness and the direction of polishing lines on the bending properties of a rolled AZ31 alloy.To this end,three-point bending tests were performed on one sample without polishing lines(SS sample)and two samples with polishing lines—one in which the polishing lines were parallel to the rolling direction(RS-RD sample)and the other in which they were parallel to the transverse direction(RS-TD sample).In all three samples,macrocracks were formed in the width direction on the outer surface,where tensile stress was predominantly generated in the longitudinal direction.However,the macrocracks formed in the SS sample were curved because of the merging of uniformly formed fine microcracks,whereas those formed in the RS-TD sample were linear owing to the formation of relatively coarse microcracks along the polishing lines.The bendability of the samples was in the order of SS>RS-RD>RS-TD,and their limiting bending depths were 4.8,4.6,and 4.4 mm,respectively.In the presence of mechanical-polishing-induced surface roughness,polishing lines perpendicular to the direction of the major stress(i.e.,tensile stress along the longitudinal direction)resulted in a greater degree of stress concentration on the outer surface of the bending specimen.This higher stress concentration promoted the formation of undesirable{10–11}contraction and{10–11}–{10–12}double twins—which typically act as crack initiation sites—and thereby facilitated crack generation and propagation.Consequently,the surface roughness caused premature fracture during bending deformation,which,in turn,caused deterioration of the bendability of the rolled Mg alloy.

An investigation on multilayer shape memory polymers under finite bending through nonlinear thermo-visco-hyperelasticity

This study presents a semi-analytical solution to describe the behavior of shape memory polymers(SMPs) based on the nonlinear thermo-visco-hyperelasticity which originates from the concepts of internal state variables and rational thermodynamics.This method is developed for the finite bending of multilayers in a dual-shape memory effect(SME) cycle.The layer number and layering order are investigated for two different SMPs and a hyperelastic material.In addition to the semi-analytical solution,the finite element simulation is performed to verify the predicted results,where the outcomes demonstrate the excellent accuracy of the proposed solution for predicting the behavior of the multilayer SMPs.Since this method has a much lower computational cost than the finite element method(FEM),it can be used as an effective tool to analyze the SMP behavior under different conditions,including different materials,different geometries,different layer numbers,and different layer arrangements.

Research on the Bending Impact Resistance and Transverse Fracture Characteristics of Bamboo under the Action of Falling Weight

Drop weight impact tester was used to accurately measure the bending impact resistance of various parts of Phyllostachys edulis,commonly known as moso bamboo,with a growth cycle of 3–8 years.Cellulose crystallinity in the bottom(B),middle(M)and top(T)of bamboo at different ages was calculated using peak height analysis in X-ray diffraction.Heatmap of Spearman correlation analysis was used to represent the correlation between chemical composition and impact mechanics.The breaking load(BL),fracture energy(FE)and impact deflection(ID)of 3–8-year-old bamboo were found to be in the range of~670–2120 N,~5.17–15.55 J,and~3.60–~17.76 mm,respectively.As the growth period of bamboo rises,the cellulose crystallinity at the B and T decreases first and then increases,while that for the M increases first and then remains stable.Similarly,the bending impact performance of bamboo was found to become stable with its growth and age.The flexural impact and toughness of the 4-year-old bamboo base material were better than other specimens.The enhancement in the bending impact properties of bamboo at different growth periods was influenced by the lignin content,while the value of FE was mainly positively correlated with ash,cold and hot water extracts and benzyl alcohol content.However the content of holocellulose and pentosan,air-dry density and,base density negatively influenced the FE.With the change in the height of the bamboo,the correlation between its impact mechanical properties and chemical composition gradually decreased.This study provides data support and theoretical basis for the age-appropriate thinning and application of moso bamboo.

Bending and Free Vibration Analysis of Porous-Functionally-Graded(PFG)Beams Resting on Elastic Foundations

The bending and free vibration of porous functionally graded(PFG)beams resting on elastic foundations are analyzed.The material features of the PFG beam are assumed to vary continuously through the thickness according to the volume fraction of components.The foundation medium is also considered to be linear,homogeneous,and isotropic,and modeled using the Winkler-Pasternak law.The hyperbolic shear deformation theory is applied for the kinematic relations,and the equations of motion are obtained using the Hamilton’s principle.An analytical solution is presented accordingly,assuming that the PFG beam is simply supported.Comparisons with the open literature are implemented to verify the validity of such a formulation.The effects of the elastic foundations,porosity volume percentage and span-to-depth ratio are finally discussed in detail.

Exceptional-point-enhanced sensing in an all-fiber bending sensor

An exceptional-point(EP)enhanced fiber-optic bending sensor is reported.The sensor is implemented based on paritytime(PT)-symmetry using two coupled Fabry-Perot(FP)resonators consisting of three cascaded fiber Bragg gratings(FBGs)inscribed in an erbium-ytterbium co-doped fiber(EYDF).The EP is achieved by controlling the pumping power to manipulate the gain and loss of the gain and loss FP resonators.Once a bending force is applied to the gain FP resonator to make the operation of the system away from its EP,frequency splitting occurs,and the frequency spacing is a nonlinear function of the bending curvature,with an increased slope near the EP.Thus,by measuring the frequency spacing,the bending information is measured with increased sensitivity.To achieve high-speed and high-resolution interrogation,the optical spectral response of the sensor is converted to the microwave domain by implementing a dual-passband microwave-photonic filter(MPF),with the spacing between the two passbands equal to that of the frequency splitting.The proposed sensor is evaluated experimentally.A curvature sensing range from 0.28 to 2.74 m^(−1) is achieved with an accuracy of 7.56×10^(−4 )m^(−1 )and a sensitivity of 1.32 GHz/m^(−1),which is more than 4 times higher than those reported previously.

Accounting for speckle-scale beam bending in classical ray tracing schemes for propagating realistic pulses in indirect drive ignition conditions

We propose a semi-analytical modeling of smoothed laser beam deviation induced by plasma flows.Based on a Gaussian description of speckles,the model includes spatial,temporal,and polarization smoothing techniques,through fits coming from hydrodynamic simulations with a paraxial description of electromagnetic waves.This beam bending model is then incorporated into a ray tracing algorithm and carefully validated.When applied as a post-process to the propagation of the inner cone in a full-scale simulation of a National Ignition Facility(NIF)experiment,the beam bending along the path of the laser affects the refraction conditions inside the hohlraum and the energy deposition,and could explain some anomalous refraction measurements,namely,the so-called glint observed in some NIF experiments.

Analysis of the Characteristics of Materials Obtained by Recycling Scrap Metal in Guinea

The aim of this study was to determine the quality of rebar produced from recycled scrap metal collected throughout the country,and imported rebar sold in the Republic of Guinea.To do this,the samples were subjected to various mechanical tests involving traction,bending and microscopic analysis.In the Lambanyi and Casse Sonfonia samples,all the tensile strength values for diameters 12,14 and 16 were above 550 MPa.Conversely,the iron samples from Baillobaye and the 10 mm diameters of the samples from Casse Sonfonio and Lambanyi have less appreciable values.The limits of elasticity were determined.The various values found vary more or less from the conventional yield strength of the NF A35-016 reference supplied by CBITEC,which is 500 MPa.Microscopic analysis gives us an insight into the internal structure of the iron samples used.This study may provide the company and the vendors with an alternative for their improvements.

Speed and surface steepness affect internal tibial loading during running

Background:Internal tibial loading is influenced by modifiable factors with implications for the risk of stress injury.Runners encounter varied surface steepness(gradients)when running outdoors and may adapt their speed according to the gradient.This study aimed to quantify tibial bending moments and stress at the anterior and posterior peripheries when running at different speeds on surfaces of different gradients.Methods:Twenty recreational runners ran on a treadmill at 3 different speeds(2.5 m/s,3.0 m/s,and 3.5 m/s)and gradients(level:0%;uphill:+5%,+10%,and+15%;downhill:-5%,-10%,and-15%).Force and marker data were collected synchronously throughout.Bending moments were estimated at the distal third centroid of the tibia about the medial-lateral axis by ensuring static equilibrium at each 1%of stance.Stress was derived from bending moments at the anterior and posterior peripheries by modeling the tibia as a hollow ellipse.Two-way repeated-measures analysis of variance were conducted using both functional and discrete statistical analyses.Results:There were significant main effects for running speed and gradient on peak bending moments and peak anterior and posterior stress.Higher running speeds resulted in greater tibial loading.Running uphill at+10%and+15%resulted in greater tibial loading than level running.Running downhill at-10%and-15%resulted in reduced tibial loading compared to level running.There was no difference between+5%or-5%and level running.Conclusion:Running at faster speeds and uphill on gradients≥+10%increased internal tibial loading,whereas slower running and downhill running on gradients≥-10%reduced internal loading.Adapting running speed according to the gradient could be a protective mechanism,providing runners with a strategy to minimize the risk of tibial stress injuries.

Analysis of bending and buckling of pre-twisted beams:A bioinspired study

Twisting chirality is widely observed in artificial and natural materials and structures at different length scales. In this paper, we theoretically investigate the effect of twisting chiral morphology on the mechanical properties of elas- tic beams by using the Timoshenko beam model. Particular attention is paid to the transverse bending and axial buckling of a pre-twisted rectangular beam. The analytical solution is first derived for the deflection of a clamped-free beam under a uniformly or periodically distributed transverse force. The critical buckling condition of the beam subjected to its self- weight and an axial compressive force is further solved. The results show that the twisting morphology can significantly improve the resistance of beams to both transverse bending and axial buckling. This study helps understand some phenomena associated with twisting chirality in nature and provides inspirations for the design of novel devices and structures.

Effect of Pre-strain on Microstructure and Stamping Performance of High-strength Low-alloy Steel

In this study,pre-strain ranging from 0 to 0.12 was applied through uniaxial tension on high-strength low-alloy(HSLA)specimens with four kinds of grain size.Effect of pre-strain and grain size on me-chanical property was investigated through tensile tests.Microstructures of the pre-strained and tensile tested samples were analyzed,respectively.The 30.8°v-bending and following flattening,as well as Erichson cupping tests,were performed on the pre-strained samples.Results show the elongation ratio of grain and dislocation density increases with pre-strain.Yielding platform is removed when pre-strain is larger than 0.06 while yielding plateau period decreases with pre-strain less than 0.06 due to reduction of pinning effect.The 30.8°v-bending and the following flattening tests are successfully accomplished on all the pre-strained samples with different grain size.Decrease in grain size,along with increase in pre-strain,causes increase in strength and decrease in elongation rate as well as cupping value.Pre-strain causes very slight effect on bending ability,much less than that on mechanical property and cupping test value.Reciprocal impact of the pre-strain and grain size on HSLA steel deformability is inconspicuous.