Experimental and Numerical Research on Deformation Behavior of Thin-Walled and Large Expansion Ratio Guide Vane Liner in Hydroforming Process

Some tube hydroforming process tests and further research work were conducted to manufacture hollow guide vane liners( made of super alloy GH3030).The relative thickness( t0/ OD) of the tubular blank is approximately 0. 01,and the maximum expansion ratio( Dmax/ OD) of the needed part is more than 40%,and the length to diameter ratio of the expansion regionis more than 3. 0. It is very hard to manufacture this kind of ultra-thin-wall,curved axis and large expansion ratio tubular part without fracture and wrinkles. The success of the process is highly dependent on useful wrinkles with appropriate internal pressure and axial feeding. A simplified finite element model and a theoretical model are used for detecting the deformation behavior and forming laws. Further study results demonstrate that the useful wrinkles do not appear at the same time and middle-wrinkles need bigger axial force than tube-end-wrinkles and feeding-wrinkles. The wrinkles can transfer bigger axial force after its wave peak has come into contact with the die inner surface. The thickness thinning rate of the element at the peak is bigger than that at the trough. With the increase of the axial and hoop stress ratio,the critical buckling stress also increases. Microstructure examination results show that the grain size in the maximum thinning zone has been stretched and refined after the large deformation and annealing treatment.The process is feasible and the finished part is qualified.

Side Wall Effects on the Hydrodynamics of a Floating Body by ImageGreen Function Based on TEBEM

A novel numerical model based on the image Green function and first-order Taylor expansion boundary element method(TEBEM), which can improve the accuracy of the hydrodynamic simulation for the non-smooth body, was developed to calculate the side wall effects on first-order motion responses and second-order drift loads upon offshore structures in the wave tank. This model was confirmed by comparing it to the results from experiments on hydrodynamic coefficients, namely the first-order motion response and second-order drift load upon a hemisphere, prolate spheroid, and box-shaped barge in the wave tank. Then,the hydrodynamics of the KVLCC2 model were also calculated in two wave tanks with different widths. It was concluded that this model can predict the hydrodynamics for offshore structures effectively, and the side wall has a significant impact on the firstorder quantities and second-order drift loads, which satisfied the resonant rule.

Reduction of the residual stresses in cold expanded thick-walled cylinders by plastic compression

We suppose that in order to maintain high accuracy of holes and to lower residual stresses after cold expansion of thick-walled cylinders, which undergo cross-section plastic deformation, it is necessary to perform axial plastic compression and subsequent cold expansion with small interferences. To test this hypothesis, we studied hoop, radial and axial residual stresses in cylinders made of carbon steel AISI 1050 with hole diameter of 5 mm, outer diameter of 15 mm and length of 30 mm by Sachs method as well as accuracy of expanded holes. It is found that double cold expansion with total interference equal to 5.1% generates hoop residual stresses with largest absolute value equal to 284 MPa and ensures high holes accuracy(IT7). After plastic compression with strain equal to 0.5 and 1% the mentioned stresses reduced to 120 and 75 MPa respectively,and accuracy of the holes reduced as well. Subsequent cold expansion with small interference equal to 0.9% helps to restore holes accuracy(IT7)gained by double cold expansion and ensure that absolute value of hoop residual stresses(177 MPa) is lower compared to double cold expansion.

Simulation Analysis of Torsion Beam Hydroforming Based on the Fluid-Solid Coupling Method

Hydroformed parts are widely used in industrial automotive parts because of their higher stiffness and fatigue strength and reduced weight relative to their corresponding cast and welded parts.This paper reports a hydraulicforming experimental platform for rectangular tube fittings that was constructed to conduct an experiment on the hydraulic forming of rectangular tube fittings.A finite element model was established on the basis of the fluid–solid coupling method and simulation analysis.The correctness of the simulation analysis and the feasibility of the fluid–solid coupling method for hydraulic forming simulation analysis were verified by comparing the experimental results with the simulation results.On the basis of the simulation analysis of the hydraulic process of the torsion beam using the fluid–solid coupling method,a sliding mold suitable for the hydroforming of torsion beams was designed for its structural characteristics.The effects of fluid characteristics,shaping pressure,axial feed rate,and friction coefficient on the wall thicknesses of torsions beams during formation were investigated.Fluid movement speed was related to tube deformation.Shaping pressure had a significant effect on rounded corners and straight edges.The axial feed speed was increased,and the uneven distribution of wall thicknesses was effectively improved.Although the friction coefficient had a nonsignificant effect on the wall thickness of the ladder-shaped region,it had a significant influence on a large deformation of wall thickness in the V-shaped area.In this paper,a method of fluid-solid coupling simulation analysis and sliding die is proposed to study the high pressure forming law in torsion beam.

缓冲层-桩板墙组合支护膨胀土边坡现场试验研究

为研究缓冲层对桩板墙结构支护膨胀土边坡的力学与变形特性的影响,以湖北当阳某铁路膨胀土边坡的桩板墙-缓冲层[包括聚苯乙烯泡沫(EPS)缓冲层和袋装砂石缓冲层2种]组合支护结构为对象,通过实施现场试验,分析气候环境作用下该组合支护结构中的土体湿度、桩身位移、板后土压力及桩与板弯矩的变化规律,揭示不同缓冲层情况下膨胀土边坡-缓冲层-桩板墙组合支护结构的相互作用及其协同的力学与变形关系.结果表明:相比于袋装砂石缓冲层,EPS缓冲层能够更有效地降低侧向膨胀压力,在本试验中测得最大消减率为69%.同时,EPS缓冲层能够及时响应气候环境引起的膨胀土胀缩变化,继而动态改善板后侧向总土压力的分布,而袋装砂石缓冲层对气候环境的响应能力明显相对较弱.膨胀土边坡-EPS缓冲层-桩板墙结构三者之间能够形成稳定的协调相互作用,进而降低膨胀土膨胀特性对桩间板弯矩的影响.

基于DPM-to-VOF方法的液滴射流撞壁过程研究

喷淋雾化被广泛应用于核动力设备中,以保证其安全稳定运行。喷淋时,部分液滴会撞击设备壁面,以液膜的形式进行扩展和演变。基于Fluent软件的离散相-连续相转换(DPM-to-VOF,DTV)方法进行了液滴射流撞壁研究,使用两液滴滴落过程试验图像验证了模拟方法的准确性,研究了液滴射流注入速度、入射角度对壁面液膜形态的影响规律,得到了液滴溅射率随入射条件的变化情况,并分析了液滴撞击壁面时重力、表面张力、速度分量等对液膜形态扩展过程、液滴溅射率的影响。研究发现,增大注入速度能加大对液膜的扰动,液膜与壁面的接触面积显著增大,液膜区宽度和高度增加;增大入射角度对液膜形态的改变影响较大,体现在液膜区宽度增加和液膜区高度减小,液膜表面稳定性减低。溅射率随着注入速度和入射角度的增大而增大,其中,入射角度对溅射率的影响更大。

Homotopy analysis solutions for the asymmetric laminar flow in a porous channel with expanding or contracting walls

In this paper, the asymmetric laminar flow in a porous channel with expanding or contracting walls is investigated. The governing equations are reduced to ordinary ones by using suitable similar transformations. Homotopy analysis method （HAM） is employed to obtain the expres- sions for velocity fields. Graphs are sketched for values of parameters and associated dynamic characteristics, especially the expansion ratio, are analyzed in detail.

Active earth pressure acting on retaining wall considering anisotropic seepage effect

This paper presents a general solution for active earth pressure acting on a vertical retaining wall with a drainage system along the soil-structure interface. The backfill has a horizontal surface and is composed of cohesionless and fully saturated sand with anisotropic permeability along the vertical and horizontal directions. The extremely unfavourable seepage flow on the back of the retaining wall due to heavy rainfall or other causes will dramatically increase the active earth pressure acting on the retaining walls, increasing the probability of instability. In this paper, an analytical solution to the Laplace differential governing equation is presented for seepage problems considering anisotropic permeability based on Fourier series expansion method. A good correlation is observed between this and the seepage forces along a planar surface generated via finite element analysis. The active earth pressure is calculated using Coulomb's earth pressure theory based on the calculated pore water pressures. The obtained solutions can be degenerated into Coulomb's formula when no seepage exists in the backfill. A parametric study on the influence of the degree of anisotropy in seepage flow on the distribution of active earth pressure behind the wall is conducted by varying ratios of permeability coefficients in the vertical and horizontal directions,showing that anisotropic seepage flow has a prominent impact on active earth pressure distribution. Other factors such as effective internal friction angle of soils and soil/wall friction conditions are also considered.

Biomechanical Analysis of a Radial Expansion Mechanism of Intestinal Robot Coupling with Hyperelastic Intestinal Wall

This paper proposes a new type of radial expansion mechanism by adopting the scissor type telescopic design for intestinal robot to meet the requirements of the intestinal robot’s movement and residence in the intestinal tract.The robot’s maximum expansion radius is up to 25mm,which can well adapt to the intestinal tract with different diameters.At first,the mathematical model of the scissors-type telescopic mechanism(STM)is established to further study its dynamics characteristics by theoretical analysis and simulation.Then,in order to study the coupling effect between the STM and intestinal wall,the strain-energy function of Fung-type is used to establish the constitutive model of intestinal wall.Moreover,aimed at solving the non-convergence problem caused by the selection of material parameters in general Fung-type model,the restrictions for selecting material parameters were given by using positive definite matrix theory.Furthermore,the motion coupling characteristics between the mechanism and intestinal wall were analyzed by using the finite element method.The result shows that if the expansion radius of the STM exceeds a certain value,the intestinal wall may reach its deformation limit,which means that the maximum rotating angle of the three-claw butterfly disc of STM can be decided based on the maximum deformation stress of the intestinal wall.Therefore,it provides a design basis for formulating a reasonable expansion radius in mechanism control to avoid damage to the intestinal wall.

典型控流调压阀后突扩体的压力特性

为了研究突扩体对控流调压阀门的增压减振作用,以典型控流调压阀门(活塞式调流阀和固定式锥形阀)为研究对象,采用物模试验和三维数值模拟相结合的研究方法,重点对2类阀门在不同突扩体型、阀门开度及空化强度下的阀后流态及管壁压力特性进行了观测分析,探究突扩比与阀后稳定压力的定量关系,试验阀门通径为150 mm,阀门直径为150~370 mm,突扩体长度为1000 mm.结果表明,突扩体能提升阀后管壁时均压力、减弱压力脉动的基本原理是水垫层效应.综合物模与数模试验结果,拟合得到了突扩比与阀后管壁稳定时均压力的关系式.突扩体可以提升阀门的工作背压,提升程度随突扩比的增大而渐缓.当突扩比为4.00时,阀后管壁稳定时均压力的增幅已非常平缓,趋于稳定.不同阀型试验结果差异小,说明突扩体的增压减振作用具有普适性.研究结果可供输水调压工程阀门段管道系统设计参考借鉴.

急倾斜薄矿体采场围岩及假底应力分布规律研究

急倾斜极薄矿脉是有色、黄金矿山常见的矿体形态,多采用人工假底的留矿法或削壁充填法回采,研究采动过程中围岩和人工假底的受力分布对于设计假底参数和安全开采具有重要意义。以某金矿削壁充填采场为工程背景,模拟研究了人工假底及围岩采动过程中应力变化规律。上、下盘围岩采动后最大主应力和最小主应力减小,回采区域顶板应力集中。假底中心处垂直压力最小,越靠近上、下盘边壁垂直压力增加,随着采高增加,假底各部位的垂直压力增加,最后呈收敛趋势。人工假底主要是剪应力破坏,假底破坏主要是上、下盘高水平应力未作用在同一轴线而产生的剪应力造成的。根据散体侧压力和采动应力变化规律,提出在采场内每隔10m利用混凝土铺底,增加人工假底中混凝土强度及垂直方向的配筋,提高假底抗剪强度,从而提高深部采场回采的安全性和人工假底的稳固性。

基于在线监控数据分析的水冷壁膨胀特性

锅炉水冷壁的膨胀状态影响火电机组的稳定和安全运行。基于在线监控数据对某超超临界机组锅炉的膨胀特性进行评价。基于最小二乘法对正常运行阶段锅炉测点膨胀位移数据进行拟合,通过膨胀位移波动率展现正常运行阶段中测点膨胀情况。结果表明,锅炉启动阶段、停炉阶段膨胀量均随时间急剧变化,而正常运行阶段膨胀监控值则围绕热态膨胀设计值波动。冷灰斗处测点Z轴方向位移平均拟合值较热态设计值减小24.73 mm,这可能源于锅炉水冷壁通过屈服或变形,吸收了部分膨胀。同一标高不同测点水平方向膨胀情况存在差异。5号测点Y轴位移波动率δ基本分布在±5%内,而6号测点仅有33.05%的监控膨胀值波动率分布在±5%内,这可能源于燃烧动力场分布不均匀。因此,水冷壁膨胀监控分析能够有效反映锅炉设备状态。

高焓流场球头外形气动热试验研究

再入地球大气层时,飞行器的再入速度极高,面临严重的气动加热问题。为了研究高焓流动导致的热化学非平衡现象,在高焓膨胀风洞FD-14X中开展了球头外形的热流测量试验以及CFD仿真模拟。FD-14X为中国空气动力研究与发展中心新建成的高焓膨胀风洞,速度模拟能力达到第二宇宙速度,总温模拟能力超过10000 K,能够产生总焓70 MJ/kg的试验气体。试验来流总焓16.9~63.5 MJ/kg,球头直径20~50 mm,流场采用自发光拍照,同时CFD仿真采用Park双温非平衡模型计算球头绕流流场。试验与仿真结果表明:来流总焓大于5 MJ/kg时,球头绕流场存在显著的热化学非平衡现象;304钢模型壁面在来流总焓小于20 MJ/kg时表现为非催化壁面特性,在来流总焓大于30 MJ/kg时表现为催化壁面特性;当球头表面镀氧化锆膜、来流总焓49.5 MJ/kg时,球头壁面表现为非催化壁面特性。

Control of Cell Wall Extensibility during Pollen Tube Growth

In this review, we address the question of how the tip-growing pollen tube achieves its rapid rate of elongation while maintaining an intact cell wall. Although turgor is essential for growth to occur, the local expansion rate is controlled by local changes in the viscosity of the apical wall. We focus on several different structures and underly- ing processes that are thought to be major participants including exocytosis, the organization and activity of the actin cytoskeleton, calcium and proton physiology, and cellular energetics. We think that the actin cytoskeleton, in particular the apical cortical actin fringe, directs the flow of vesicles to the apical domain, where they fuse with the plasma mem- brane and contribute their contents to the expanding cell wall. While pH gradients, as generated by a proton-ATPase located on the plasma membrane along the side of the clear zone, may regulate rapid actin turnover and new polymeri- zation in the fringe, the tip-focused calcium gradient biases secretion towards the polar axis. The recent data showing that exocytosis of new wall material precedes and predicts the process of cell elongation provide support for the idea that the intussusception of newly secreted pectin contributes to decreases in apical wall viscosity and to cell expansion. Other prime factors will be the localization and activity of the enzyme pectin methyl-esterase, and the chelation of calcium by pectic acids. Finally, we acknowledge a role for reactive oxygen species in the control of wall viscosity.

自张式膨胀管技术的研究与应用

孔内膨胀管钻探技术是保障复杂地层孔壁稳定的有效技术之一。本文针对易出现缩径、坍塌、掉块的强水敏性地层,提出了一种自张式膨胀管护壁方法,并根据该方法的护壁原理研制了相适配的新型扩孔钻具、膨胀管及膨胀管投送装置,在不改变钻孔结构的情况下,对复杂孔段进行局部扩孔,投送膨胀管借助自身张力自然弹开而固定在相应的扩孔段,实现钻进时护壁。通过室内及现场试验对机具进行了优化,最终取得了良好的应用效果。试验证明:该方法操作简单可靠、易于定位,相较于水泥浆护壁具有处理速度快、停待时间短、减少重复处理等优势,适用于岩心钻探领域多孔段复杂地层的固壁与护壁,有利于降低孔内事故处理的成本、提高钻进效率,具有较好的推广应用价值。

内壁扩张角度对冲压旋转爆轰燃烧室工作特性影响的数值研究

为研究内壁扩张角度对冲压旋转爆轰燃烧室工作特性的影响,构建了内壁扩张角度从0°~6°变化的5种扩张型燃烧室,基于乙烯-空气对带有凹腔结构的冲压旋转爆轰燃烧室进行三维数值模拟,分析了不同扩张角度下燃烧室的流场特征。计算结果表明:采用扩张型流道可有效减弱新鲜燃料层内的提前燃烧现象,随着扩张角度增大,爆轰波波头高度增加,爆轰波传播稳定性增强;扩张型流道对爆轰波后燃烧产物起到整体加速作用,并未起到整流作用;凹腔结构中涡核中心随着扩张角度的增大逐渐向凹腔后缘壁面移动,回流进入凹腔底部的新鲜燃料增多,凹腔对主流区新鲜燃料卷吸作用增强;采用扩张型流道后,燃烧室凹腔段总压增益和燃烧室出口总压均随扩张角度的增大而降低。

相向对撞壁面射流分区及扩展数值模拟

为了揭示相向对撞壁面射流中径向和垂向射流特性,采用RNG k-ε模型对相向对撞壁面射流进行三维精细模拟,分析相向对撞射流产生的径向射流、垂向射流的分区结构和扩展率,探讨初始雷诺数和喷嘴间距对射流扩展率的影响。结果表明,径向射流和垂向射流分区结构类似,但流场中形成的径向和垂向漩涡影响范围不同。射流初始雷诺数对径向射流扩展率影响不明显,喷嘴间距对径向和垂向射流的扩展率影响明显,且喷嘴间距越大,径向射流和垂向射流的扩展率越大。此外,喷嘴间距对射流发育过程有一定影响,喷嘴间距越小,射流到达最大速度点所需时间越短、射流发育过程越快。

REFLECTION OF OBLIQUE INCIDENT WAVES BY PERFORATED CAISSONS WITH TRAVERSE WALL

The interaction of oblique incident waves with infinite number of perforated caissons is investigated. The fluid domain is divided into infinite sub-domains by the caissons, and eigen-function expansion is applied to expand velocity potentials in each domain. A phase relation is introduced for wave oscillation in each caisson, and the structure geometry is considered in constructing the models of reflection waves. The reflected waves with the present analysis include all of the waves traveling in different directions when incident wave period is short. Numerical examinations show that velocities at the inner and outer sides of the front walls of caissons ase close to each other, and reflection coefficients satisfy the energy conservation relation very well when porous effect parameter is infinite. Numerical results show that the reflection coefficients of oblique incident waves are smaller for shorter caissons at low frequency, and decrease with the increase of wave incident angle.

Microanalysis of Plant Cell Wall Polysaccharides

Oligosaccharide Mass Profiling （OLIMP） allows a fast and sensitive assessment of cell wall polymer structure when coupled with Matrix Assisted Laser Desorption Ionisation Time Of Flight Mass Spectrometry （MALDI-TOF MS）. The short time required for sample preparation and analysis makes possible the study of a wide range of plant organs, revealing a high degree of heterogeneity in the substitution pattern of wall polymers such as the cross-linking glycan xyloglucan and the pectic polysaccharide homogalacturonan. The high sensitivity of MALDI-TOF allows the use of small amounts of samples, thus making it possible to investigate the wall structure of single cell types when material is collected by such methods as laser micro-dissection. As an example, the analysis of the xyloglucan structure in the leaf cell types outer epidermis layer, entire epidermis cell layer, palisade mesophyll cells, and vascular bundles were investigated. OLIMP is amenable to in situ wall analysis, where wall polymers are analyzed on unprepared plant tissue itself without first isolating cell walls. In addition, OLIMP enables analysis of wall polymers in Golgi-enriched fractions, the location of nascent matrix polysaccharide biosynthesis, enabling separation of the processes of wall biosynthesis versus post-deposition apoplastic metabolism. These new tools will make possible a semi-quantitative analysis of the cell wall at an unprecedented level.

无固相冲洗液防塌护壁性能强化改进试验研究

为了改善地质岩心钻探中无固相冲洗液的护壁防塌性能,筛选了脂环类固化剂EPR,脂肪类固化剂DETA、AEP,芳香类固化剂PU,酰胺类固化剂PET共5五种固化剂。利用固化剂可以改进被固化物质的膜硬度、膜附着力、膜耐候性和增加光泽度的特性,向无固相冲洗液中添加固化剂以改善其防塌护壁性能,通过岩心浸泡试验和线性膨胀量试验,确定固化剂EPR和PU具有较好的护壁防塌性能改善作用。然后对EPR和PU进行复配,通过岩心浸泡试验结果得出最优比例为EPR∶PU=1∶4,最后通过线性膨胀量测试和流变性能测试,确定固化剂配方的最优加量为0.2%。确定无固相冲洗液配方为清水+0.5%聚丙烯酰胺+0.04%EPR+0.16%PU,该配方在对冲洗液流变性能影响较小的前提下,改善了冲洗液的护壁防塌性能。