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.

Bending Failure Mode and Prediction Method of the Compressive Strain Capacity of A Submarine Pipeline with Dent Defects

A dent is a common type of defects for submarine pipeline.For submarine pipelines,high hydrostatic pressure and internal pressure are the main loads.Once pipelines bend due to complex subsea conditions,the compression strain capacity may be exceeded.Research into the local buckling failure and accurate prediction of the compressive strain capacity are important.A finite element model of a pipeline with a dent is established.Local buckling failure under a bending moment is investigated,and the compressive strain capacity is calculated.The effects of different parameters on pipeline local buckling are analyzed.The results show that the dent depth,external pressure and internal pressure lead to different local buckling failure modes of the pipeline.A higher internal pressure indicates a larger compressive strain capacity,and the opposite is true for external pressure.When the ratio of external pressure to collapse pressure of intact pipeline is greater than 0.1,the deeper the dent,the greater the compressive strain capacity of the pipeline.And as the ratio is less than 0.1,the opposite is true.On the basis of these results,a regression equation for predicting the compressive strain capacity of a dented submarine pipeline is proposed,which can be referred to during the integrity assessment of a submarine pipeline.

Cryogenic springback of 2219-W aluminum alloy sheet through V-shaped bending

A V-shaped bending device was established to evaluate the effects of temperature and bending fillet radius on springback behavior of 2219-W aluminum alloy at cryogenic temperatures.The cryogenic springback mechanism was elucidated through mechanical analyses and numerical simulations.The results indicated that the springback angle at cryogenic temperatures was greater than that at room temperature.The springback angle increased further as the temperature returned to ambient conditions,attributed to the combined effects of the “dual enhancement effect” and thermal expansion.Notably,a critical fillet radius made the springback angle zero for 90° V-shaped bending.The critical fillet radius at cryogenic temperatures was smaller than that at room temperature,owing to the influence of temperature variations on the bending moment ratio between the forward bending section at the fillet and the reverse bending section of the straight arm.

Analysis of deformation mechanisms in magnesium single crystals using a dedicated four-point bending tester

In this study,we explored the deformation mechanisms of Mg single crystals using a combination of scanning electron microscopy and electron backscattered diffraction in conjunction with a dedicated four-point bending tester.We prepared two single-crystal samples,oriented along the<1120>and<1010>directions,to assess the mechanisms of deformation when the initial basal slip was suppressed.In the<1120>sample,the primary{1012}twin(T1)was confirmed along the<1120>direction of the sample on the compression side with an increase in bending stress.In the<1010>sample,T1 and the secondary twin(T2)were confirmed to be along the<1120>direction,with an orientation of±60°with respect to the bending stress direction,and their direction matched with(0001)in T1 and T2.This result implies that crystallographically,the basal slip occurs readily.In addition,the<1010>sample showed the double twin in T1 on the compression side and the tertiary twin along the<1010>direction on the tension side.These results demonstrated that the maximum bending stress and displacement changed significantly under the bend loading because the deformation mechanisms were different for these single crystals.Therefore,the correlation between bending behavior and twin orientation was determined,which would be helpful for optimizing the bending properties of Mg-based materials.

Bending strength degradation of a cantilever plate with surface energy due to partial debonding at the clamped boundary

This paper investigates the bending fracture problem of a micro/nanoscale cantilever thin plate with surface energy,where the clamped boundary is partially debonded along the thickness direction.Some fundamental mechanical equations for the bending problem of micro/nanoscale plates are given by the Kirchhoff theory of thin plates,incorporating the Gurtin-Murdoch surface elasticity theory.For two typical cases of constant bending moment and uniform shear force in the debonded segment,the associated problems are reduced to two mixed boundary value problems.By solving the resulting mixed boundary value problems using the Fourier integral transform,a new type of singular integral equation with two Cauchy kernels is obtained for each case,and the exact solutions in terms of the fundamental functions are determined using the PoincareBertrand formula.Asymptotic elastic fields near the debonded tips including the bending moment,effective shear force,and bulk stress components exhibit the oscillatory singularity.The dependence relations among the singular fields,the material constants,and the plate's thickness are analyzed for partially debonded cantilever micro-plates.If surface energy is neglected,these results reduce the bending fracture of a macroscale partially debonded cantilever plate,which has not been previously reported.

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.

抗桥粒芯蛋白1、3抗体及大疱性类天疱疮180、230抗体联合检测诊断大疱性皮肤病的应用价值

目的 探讨抗桥粒芯蛋白1、3(Dsg1、3)抗体及大疱性类天疱疮180、230(BP180、230)抗体联合检测在大疱性皮肤病临床诊断中的应用价值。方法 自2020年3月至2023年1月,纳入郑州大学第一附属医院收治的经组织病理结果、直接免疫荧光检测确诊的大疱性皮肤病患者88例为观察组,选取本院同期健康体检者76名为对照组。分析两组Dsg1、Dsg3、BP180、BP230抗体的阳性检出情况;分析观察组血清Dsg1、Dsg3、BP180、BP230抗体标本诊断类型占比及观察组不同年龄组大疱性皮肤病疾病类型阳性率占比;绘制ROC曲线分析Dsg1、Dsg3、BP180、BP230抗体单一及联合检测对大疱性皮肤病的诊断价值。结果 两组血清Dsg1、Dsg3、BP180、BP230抗体阳性率比较差异具有统计学意义(P<0.05)。据Dsg1、Dsg3、BP180、BP230抗体检测结果,诊断类型:BP、PV、PF、PF+BP、PV+BP阳性率分别为32.95%、20.45%、11.36%、7.95%、3.41%。其中BP阳性率占比最高,PV+BP阳性率占比最低,两者比较差异具有统计学意义(P<0.05)。>60岁组BP阳性率高于≤60岁组,PV及PF阳性率低于≤60岁组,差异有统计学意义(P<0.05)。Dsg1、Dsg3、BP180、BP230抗体联合检测对大疱性皮肤病灵敏度、特异度分别为91.02%、88.66%,AUC(95%CI)为0.821(0.745~0.911),均高于上述抗体单一检测(P<0.05)。结论 Dsg1、Dsg3、BP180、BP230抗体在大疱性皮肤病诊断中具有重要参考价值,且联合检测可提高诊断的准确性;大疱性皮肤病患者年龄和抗体类型之间也存在一定的关联,联合检测Dsg1、Dsg3、BP180、BP230抗体有助于大疱性皮肤病进行更精细的诊断和治疗。

选择性360°和180°微脉冲激光小梁成形术治疗原发性开角型青光眼的效果差异研究

对比选择性360°和180°微脉冲小梁成形术(MLT)对原发性开角型青光眼患者治疗的效果差异。方法 将2020年2月到2023年2月到我院治疗的80例原发性开角型青光眼患者根据入院单双日分为观察组(单日组41例)和对照组(双日组39例)。分别行360°微脉冲小梁成形术和180°微脉冲小梁成形术进行治疗,对比疗效差异。结果 ①两组患者术前、术后1h、术后1d、6个月眼压无差异(P>0.05);术后1周、术后1个月、3个月有差异(P<0.05);②两组患者术前、术后1h、术后1d、术后1周、术后1个月、3个月、6个月患眼视力水平无明显差异(P>0.05)。结论 选择性360°和选择性180°MLT都能提升原发性开角型青光眼患者的视力水平,降低眼压,可根据患者的需求辩证的选择。

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.

竖缝式鱼道90°~180°转弯段水力特性及优化研究

受鱼道进出口位置、工程地质、枢纽布置等因素限制,鱼道工程需要布置不同角度的转弯段池室,以适应复杂多变工程环境。采用数值模拟的方法,研究了同侧竖缝式鱼道不同转角α(90°≤α≤180°)的转弯段池室流场分布规律,并对不同转角池室提出了系统的优化措施。结果表明,当转弯角度α大于90°时,均出现主流冲击外侧边壁,池室中部伴有大尺度回流区的现象,并随着转弯段角度α增大,主流冲击程度加剧,回流区尺度也进一步扩大。针对上述流场问题,采用加设整流导板的措施进行优化,提出转弯角度α介于90°~140°之间时,整流较好的导板位置α_(0)/α值由1/4.0增加至1/2.8,当α介于140°~180°之间时,α_(0)/α值基本稳定于1/2.8~1/3.0之间,即随着转弯角度α的逐渐增加,较优的α_(0)/α值呈现先增加后趋于稳定的变化趋势,可为转弯段结构相似布置鱼道优化设计提供参考。

玉米转录因子ZmEREB180调控根系生长发育及耐逆的功能研究

AP2/ERF(APETALA2/ethylene-responsive factor)转录因子是植物中最大的转录因子家族之一,在调控植物生长发育、响应逆境胁迫、调节激素信号转导和物质代谢等多种生物学过程中发挥着重要作用。目前AP2/ERF超家族基因在许多植物物种中的生物学功能已经得到验证,但对玉米(Zea mays L.)中AP2/ERF基因的结构和功能的研究报道较少。前期工作中我们发现,ZmEREB180(ethylene-responsive element binding)转录因子,在鉴定的玉米六叶期(V6)、十二叶期(V12)和抽雄期(VT)等关键发育时期,根系中的表达量均存在显著差异;通过组织表达分析发现该基因主要在玉米根系中表达,且在幼根中的表达量显著高于成熟根,推测该基因可能参与玉米根系生长发育调控。本研究克隆了ZmEREB180(Gene ID:100192457)基因,结合生物信息学分析、实时荧光定量PCR(RT-qPCR)、亚细胞定位和转基因拟南芥(Arabidopsis thaliana L.)株系的耐逆表型鉴定等生物学手段,初步分析了该基因的表达模式和生物学功能。该基因包含2个外显子,编码序列全长1023 bp,编码340个氨基酸,具有AP2/ERF家族所特有的保守结构域;该基因在玉米根系中表达量最高,且在高盐、干旱、高氮和低氮等胁迫处理条件下的玉米根部皆有不同程度的诱导表达,其中,低氮处理较高氮处理具有更高的表达量和更快的响应速率;在含0.10、0.15 mol L^(-1)NaCl以及0.15、0.20和0.30 mol L^(-1)甘露醇(mannitol)的1/2 MS固体培养基上,转ZmEREB180基因拟南芥的主根长度均显著长于野生型;土壤环境中,高盐和干旱胁迫条件下的转基因植株比野生型拟南芥具有更健康的生长状态、更高的绿叶率、更低的丙二醛含量和更高的过氧化物酶活性。转录因子ZmEREB180可能在调控玉米根系生长发育方面具有积极的促进作用,并且能增强玉米植株对高盐、干旱、渗透、低氮等逆境胁迫的耐受性。本研究为下一步鉴定转录因子ZmEREB180在玉米中的生物学功能和分子机制奠定了良好的基础。

转录组分析揭示荷叶离褶伞菌多糖LDS-1抗小鼠S180肿瘤的分子机制

以荷叶离褶伞菌多糖LDS-1、甘露聚糖肽和空白对照作用下的小鼠S180肿瘤细胞为研究材料,运用RNA-Seq测序技术进行生物信息学分析,结果显示LDS-1组、甘露聚糖肽组和空白对照组分别获得8.27、 8.35和8.97 G的分析数据.高表达基因(FPKM>2 200)分析显示LDS-1主要通过下调Rplp1基因调控细胞分裂,将S180细胞停滞在G1期以抑制其分裂.差异基因分析结果显示LDS-1主要通过上调Alb、 Timp4、 Apoa1基因调节蛋白表达或者细胞黏连性,抑制S180肿瘤细胞迁移.KEGG(京都基因与基因组百科全书)通路富集结果显示, LDS-1抑制S180肿瘤生长的关键基因主要富集在过氧化物酶体增殖物激活受体(PPAR)信号通路中,上游Fabp3基因下调,激活下游Apoa1、Slc27a2和Adipoq等多个基因上调,调控S180细胞的脂质代谢和胆固醇代谢. LDS-1能够通过调控高表达关键基因Rplp1,差异表达关键基因Alb、 Timp4、 Apoa1,以及PPAR信号通路抑制S180肿瘤细胞的增殖分裂、能量获取和迁移侵袭.

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.

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.

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.

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.

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.

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.