横向滑坡载荷作用下埋地PE管道的损伤数值模拟

埋地燃气输送管道服役环境复杂,其中滑坡地质灾害严重威胁管道的服役安全。以埋地聚乙烯(polyethylene,PE)管道为研究对象,利用ABAQUS有限元软件模拟了横向滑坡载荷作用下的管道损伤行为,探讨了滑坡参数(滑坡体位移量)、管道埋深以及内压对PE管力学性能的影响。研究结果表明:滑坡作用下埋地PE管最大偏移、最大Mises应力和最大主应变均位于管轴向横截对称面上。管道最大Mises应力随滑坡位移的增大而增大,管底为管道最终屈服点,屈服主要原因为管横截面被压扁变形。管道未屈服时,最大Mises应力随内压的增大呈现先减小后增大的现象,最大主应变随内压的增大而增大。最大Mises应力和最大主应变均随埋深的增大而增大。

CFRP-PE-不锈钢筋混凝土短柱的设计方法研究

进行了17个CFRP-PE-不锈钢筋混凝土短柱和8个对比试件的轴压试验,探究不锈钢种类、箍筋间距、CFRP厚度、PE厚度对该类组合柱的破坏模态、荷载-应变曲线、极限应变、极限承载力、延性的影响规律.试验结果表明:在CFRP和混凝土间设置PE垫层能提高该类组合短柱的延性和变形能力,并降低其承载力;增大CFRP厚度可提高其承载力和极限应变,但试件表现出增大的脆性;减小箍筋间距或增大钢筋强度可显著提高其承载力、峰值应变和延性.建立了有限元模型,有限元分析表明:增大PE厚径比会显著提高该类组合短柱的变形能力和延性,并降低CFRP对其承载力的影响;增大配箍率、不锈钢强度、CFRP抗拉强度、CFRP厚度可提升该类组合短柱的极限应变与承载力;提高混凝土强度会提高该类组合短柱的峰值承载力,但降低其极限应变.最终建议了该类组合短柱的延性设计方法、承载力模型和极限应变模型.

Correlations between mineral composition and mechanical properties of granite using digital image processing and discrete element method

This study investigated the correlations between mechanical properties and mineralogy of granite using the digital image processing(DIP) and discrete element method(DEM). The results showed that the X-ray diffraction(XRD)-based DIP method effectively analyzed the mineral composition contents and spatial distributions of granite. During the particle flow code(PFC2D) model calibration phase, the numerical simulation exhibited that the uniaxial compressive strength(UCS) value, elastic modulus(E), and failure pattern of the granite specimen in the UCS test were comparable to the experiment. By establishing 351 sets of numerical models and exploring the impacts of mineral composition on the mechanical properties of granite, it indicated that there was no negative correlation between quartz and feldspar for UCS, tensile strength(σ_(t)), and E. In contrast, mica had a significant negative correlation for UCS, σ_(t), and E. The presence of quartz increased the brittleness of granite, whereas the presence of mica and feldspar increased its ductility in UCS and direct tensile strength(DTS) tests. Varying contents of major mineral compositions in granite showed minor influence on the number of cracks in both UCS and DTS tests.

Rare-Element Pegmatites Rocks Rich and Li of the Aïr Massif of the Tchirozerine: Mineralogy and Chemical Composition Agadez Region-Northem Niger

The lithium potential in the Aïr massif is represented by mineral index of spodumene pegmatites and, lepidolite pegmatites. The mineral deposits of lithium occur in cluster or veins that cut the host rock or are located near the contact between the greenstone belt and granitic massif. The evidence of lithium is in the form of clusters or disseminated and stockwerk. Mineralogical characteristics show similarities between the Air Massif pegmatites and indicate the same homogenous source during the magma-generation process. The pegmatite rocks attracted the attention due to their wide exposure and composition, well appearance, and economically hosting of significant rare earth metals such as Sn and W. The mineralogical and petrographical investigations on the eight pegmatites rocks samples observed have a relative similarity, while a little difference in the shapes attributed to the ratio in the pegmatite rocks of the minerals. The occurrence of the kink band indicates the influence of the tectonic processes which affected the Aïr massif after the emplacement of late magmatic or post-magmatic pegmatites by injection into fractured rocks in the upper part of the crust. The Air Massif pegmatite has higher concentrations Li and of all trace elements except Hf and occasionally Zr, Ti, Sn and Mg of for the economic exploration.

地面沉降作用下含体积型缺陷的PE燃气管道模拟计算分析

聚乙烯(PE)管道具有良好的韧性,在城镇的燃气管道、给排水管道等方面得到广泛应用,但由于聚乙烯管道的强度较低,在安装使用过程中更容易产生缺陷或划痕,对管道性能造成影响。随着城市化的逐渐发展,我国许多发达城市均出现不同程度的区域性地面沉降,这一现象给PE管道带来了许多安全隐患。以SY市的PE燃气管道本构模型和地质条件为基础参数,对含体积型缺陷PE燃气管道进行拉伸试验,得到缺陷对管道性能的影响规律;同时,借助有限元分析软件,建立体积型缺陷管道模型,模拟分析地面沉降作用下缺陷对聚乙烯管道受力情况,得到在地面沉降作用下管体缺陷长度、缺陷周角度以及缺陷深度对管道安全性能的影响规律,为工程实际提供理论参考。

地面沉降对埋地PE燃气管道安全影响研究

近年来,地面沉降成为管道事故频发的主要原因。本文分析了PE管道失效的影响因素,基于有限元软件,探究了地面受力情况下地面沉降量及管道本身的应力情况。结果表明:PE管道失效与管道受力情况和时间有关。当地面受力强度增加,地面沉降值增加,管道受到的Von-Mises应力也增加,管道截面压缩变形严重,导致管道整体的安全系数减小。本文为地面沉降作用下的管道安全评估提供理论参考。

薄壁大口径PE管材弯曲有限元分析

对加入钢丝网的薄壁大口径PE管,运用有限元法分析其在弯曲过程中出现的内侧失稳起皱、横截面畸变等问题。采用理论分析、数值模拟和实验研究相结合的方法,对薄壁大口径PE管材弯曲进行有限元分析,在分析PE管材弯曲机理和失效形式的基础上,通过实例得出有钢丝网PE管材的弯曲所受应力主要由钢丝网承载,结合弯曲测试,发现加入钢丝网可有效增强管材的刚度、抑制管材弯曲时内侧失稳起皱和横截面畸变等现象的发生,有限元数值模拟结果与实验结果较为一致,说明有限元数值模拟分析的可靠性。

Effect of alloying elements and processing parameters on the Portevin–Le Chatelier effect of Al–Mg alloys

The effects of alloying elements and processing parameters on the mechanical properties and Portevin-Le Chatelier effect of A1-Mg alloys developed for inner auto body sheets were investigated in detail. Tensile testing was performed in various Zn and Mg contents under different annealing and cold-rolling conditions. In the results, the stress drop and reloading time of serrations increase with increasing plastic strain and exhibit a common linear relationship. The increase rates of stress drop and reloading time increase with increasing Mg or Zn content. The alloys with a greater intensity of serrated yielding generally exhibit a greater elongation. The stress drop and reloading time of serrations decrease with increasing grain size in the case of the annealed samples. The cold-rolled sample exhibits the most severe serra- tion because it initially contains a large number of grain boundaries and dislocations.

Effect of alloying elements on austempered ductile iron(ADI) properties and its process:Review

Austempered ductile iron(ADI) parts have a unique combination of high strength and toughness with excellent design flexibility and low cost. These excellent properties are directly related to its microstructure called "ausferrite" that is the result of austempering heat treatment applied to ductile irons. Alloying elements increase ADI austemperability and change speeds of austempering reactions. Thus, they can affect ADI resultant microstructure and mechanical properties. In this paper, the effects of alloying elements on ADI mechanical properties, microstructural changes, two-stage austempering reactions, processing windows, austemperability, and other aspects are reviewed.

Simulation of fluid-structure interaction in a microchannel using the lattice Boltzmann method and size-dependent beam element on a graphics processing unit

Fluid-structure interaction （FSI） problems in microchannels play a prominent role in many engineering applications. The present study is an effort toward the simulation of flow in microchannel considering FSI. The bottom boundary of the microchannel is simulated by size-dependent beam elements for the finite element method （FEM） based on a modified cou- ple stress theory. The lattice Boltzmann method （LBM） using the D2Q13 LB model is coupled to the FEM in order to solve the fluid part of the FSI problem. Because of the fact that the LBM generally needs only nearest neighbor information, the algorithm is an ideal candidate for parallel computing. The simulations are carried out on graphics processing units （GPUs） using computed unified device architecture （CUDA）. In the present study, the governing equations are non-dimensionalized and the set of dimensionless groups is exhibited to show their effects on micro-beam displacement. The numerical results show that the displacements of the micro-beam predicted by the size-dependent beam element are smaller than those by the classical beam element.

Distribution Characteristics of Minerals and Elements in Chromite Ore Processing Residue

In this paper,environmental scanning electron microscopy (ESEM) is applied to characterizing the mineral and element distribution of chromite ore processing residue (COPR).The test results show that Cr-bearing brownmillerite occurs in the rim of COPR particle,while hydroandradite with Cr(Ⅵ) in its structure presents inside the COPR particle.Periclase and calcite occur in the interstitial area.Element analyses show that Ca,Fe and Al are distributed throughout the COPR particle,and Mg exists mostly in the interstitial area or on the particle surface.A lower content of Cr is evenly distributed in the COPR particle,while slightly higher concentration of Cr occurs inside the particle.It is suggested that it will take a relatively longer time for Cr to migrate out of COPR,especially for hexavalent chromium,so the leaching time and the particle size may be two important factors to affect the release of Cr(Ⅵ).

Behaviours of Main Elements in Soil-Forming Processesof Fildes Peninsula, the Maritime Antarctic

INTRODUCTIONFildesPeninsula(62"12'S,58o58'W)ofKingGeorgeIsland,theSouthShetlandIslands,measuresabout3.5kmfromeasttowest,and7.5kmfromnorthtosouth.ThetypicalmaritimeAntarcticclimatemakesthePeninsulaoneofthewarmestandmoistestregionsinAntarctica.Accordin...

Numerical simulation of direct shear tests on mechanical properties of talus deposits based on self-adaptive PCNN digital image processing

The macro mechanical properties of materials with characteristics of large scale and complicated structural composition can be analyzed through its reconstructed meso-structures.In this work,the meso-structures of talus deposits that widely exist in the hydro-power engineering in the southwest of China were first reconstructed by small particles according to the in-situ photographs based on the self-adaptive PCNN digital image processing,and then numerical direct shear tests were carried out for studying the mechanical properties of talus deposits.Results indicate that the reconstructed meso-structures of talus deposits are more consistent with the actual situation because the self-adaptive PCNN digital image processing has a higher discrimination in the details of soil-rock segmentation.The existence and random distribution of rock blocks make the initial shear stiffness,the peak strength and the residual strength higher than those of the "pure soil" with particle size less than 1.25 cm apparently,but reduce the displacements required for the talus deposits reaching its peak shear strength.The increase of rock proportion causes a significant improvement in the internal friction angle of talus deposit,which to a certain degree leads to the characteristics of shear stress-displacement curves having a changing trend from the plastic strain softening deformation to the nonlinear strain hardening deformation,while an unconspicuous increase in cohesion.The uncertainty and heterogeneity of rock distributions cause the differences of rock proportion within shear zone,leading to a relatively strong fluctuation in peak strengths during the shear process,while movement features of rock blocks,such as translation,rotation and crossing,expand the scope of shear zone,increase the required shear force,and also directly lead to the misjudgment that the lower shear strength is obtained from the samples with high rock proportion.That,however,just explains the reason why the shear strength gained from a small amount of indoor test data is not consistent with engineering practice.

Recharge processes limit the resource elements of Qarhan Salt Lake in western China and analogues in the evaporite basins

The Qarhan Salt Lake(QSL)in western China is K-Sr-Li-B-Br-Rb multi-resource coexisting Quaternary brine deposits.Significant research efforts have been directed to the origin of K-Li resources and evolutionary history of the QSL.However,the study on the different sources,recharge processes,and differential distribution patterns for these resource elements in brine deposits is still inadequate.Therefore,we measured Li-B concentrations and H-O-Sr-B isotopic compositions of different waters(river,spring,and brine)from the QSL,combined with the reported K-Sr contents and multiple isotopes of waters,to discuss the recharge,source of K-Sr-Li-B and their spatial distributions,by analogy with other evaporite basins in the world.The results show that:(1)the K-Li-B-Sr elemental concentrations of brines and their spatial distribution in the QSL are diverse;(2)high K and Sr values are distributed in Dabuxun and Qarhan sections,respectively,which are controlled by Ca-Cl springs in the northern QSL;on the contrary,Li and B values are enriched in the Bieletan section and are charged by thermal springs in the Kunlun Mountains;(3)the formation and evolution of Ca-Cl and thermal springs constrain fundamentally on the recharge processes of K-Sr and Li-B elements in the terminal salt lakes of the Qaidam Basin(QB);(4)some analogues of recharge processes limit the resource elements of the QSL and other salt lakes(Da Qaidam,Lop Nur,Zhabuye,Atacama,and Guayatayoc)in the world provides a reference for the resource exploration in deep formation waters in the evaporite basins.

多层PET/PE复合膜热封特性试验及结构表征

为分析热封工艺对多层PET/PE复合膜热封质量及其结构的影响作用,采用直接酯化法制备了PET薄膜,通过胶黏剂将各层薄膜粘接得到了三层PET/PE复合膜,在不同参数条件下进行单因素试验,分析了温度、压强、时间对复合膜热封强度的影响,并观察了材料在不同参数下的微表面结构。结果表明,热封温度对热封强度影响较显著,薄膜表面形貌随温度的升高由平整状态转变为凹坑状,满足热封强度的最佳温度范围为160~170℃,当热封时间为0.3 s,热封压强为0.5 MPa时的热封最优强度为65 N/15 mm;绘制了压强一定下,热封强度对温度、时间的响应曲面,确定了生产实际满足热封强度要求的参数范围,为复合膜在食品、药品等包装上的应用提供了重要参数依据。

Experimental and numerical study on the influence of shaped charge liner cavity filing on jet penetration characteristics in steel targets

Penetration characteristic(size and shape of penetration craters made in high hardness ARMSTAL 30PM steel) of shaped charge jets formed after detonations of modified PG-7VM warheads was analyzed in the article. Modifications consisted in removing the frontal part of the grenade(fuse, ballistic cap and conductive cone) and introducing of the liner cavity filling made of polyacetal copolymer POM-C. The filings in the form of solid cones with three different heights(33%, 66% and 100% of H-the height of original PG-7VM liner) were placed inside of the hollow cone shaped charge liner. As opposed to the vast majority of previously published works(in which warhead optimization studies were focused on increasing of the depth of penetration in rolled homogeneous armor steel) the main aim of the presented modifications was to maximize the damage ratio(diameters of craters, inlet and outlet holes) of target perforated by shaped charge jet at the cost of the loss of part of the jet penetration capability. According to the best knowledge of the authors such approach to the use of the old PG-7VM warheads has not been analyzed so far. Taking into consideration high stock levels of PG-7VM warheads, and the fact that they are continuously being replaced by more efficient and more sophisticated high-explosive anti-tank warheads, it seems reasonable to look for alternate applications of the warheads withdrawn from the service. Thanks to the introduction of proposed modifications the warheads could be used by special forces or other assault units as directional mines or statically detonated cutting shaped charges as well as by combat engineers as universal charges used in various types of engineering or sapper works. The research included experimental penetration tests and their numerical reproduction in the LS-Dyna software with the simulation methodology defined and validated in previous works of the authors.Small differences(average error = 10-20%) were identified between the experimental and numerical results(dimensions of craters made in steel targets were compared) what confirmed the reliability of the modelling methodology and enabled its use for further optimization of the shapes of fillings. Within the analyzed variants of warheads modifications maximum diameters of penetration craters were obtained for the filling of the height of h = 2/3H. The diameters of holes in individual steel plates were increased by 164%, 70%, 65%(for the first, second and third plate, respectively) in relation to the variant without filling. The results of the study indicated that with the use of different materials of fillings and their various heights it is possible to control the shape of penetration craters pierced in the steel targets.

多层PET/PE复合膜的大尺度间歇热封工艺能耗研究

目的 分析热封设备连续加热热封工艺的能耗模型,优化设计适合大尺度热封设备的间歇加热热封工艺。方法 首先通过电热特性试验了解镍铬合金的升降温规律,拟合得到镍铬合金的升降温模型。其次分析连续加热热封工艺能耗模型,提出适用于大尺度热封设备的间歇加热热封工艺流程,并建立能耗模型。结果 以多层聚对苯二甲酸乙二醇酯/聚乙烯(PET/PE)复合膜为热封对象,以最小能耗为优化目标,计算得到最优的热封工艺流程。结论 大尺度热封设备采用间歇加热热封工艺加工可以有效减少能量损耗。

Hybrid Post-Processing Procedure for Displacement-Based Plane Elements

In the analysis of high-rise building, traditional displacement-based plane elements are often used to get the in-plane internal forces of the shear walls by stress integration. Limited by the singular problem produced by wall holes and the loss of precision induced by using differential method to derive strains, the displacement-based elements cannot always present accuracy enough for design. In this paper, the hybrid post-processing procedure based on the Hellinger-Reissner variational principle is used for improving the stress precision of two quadrilateral plane elements. In order to find the best stress field, three different forms are assumed for the displacement-based plane elements and with drilling DOF. Numerical results show that by using the proposed method, the accuracy of stress solutions of these two displacement-based plane elements can be improved.

基于有限元的室外PE管道热熔焊接工艺优化

为解决聚乙烯管道热熔焊接因室内环境与现场施工环境不一致所带来的焊接质量问题,采用Ansys有限元方法,分析不同环境对温度均匀性、熔融层厚度的影响规律并进行焊接工艺评定,建立基于熔融层厚度的焊接工艺优化模型,最后辅以拉伸实验对优化后的焊接工艺参数进行验证。结果表明,在一定的环境条件下,随着轴向距离增加,管材温度逐渐趋于环境温度;随着冷却时间增加,焊接端面温度均匀性先下降后逐渐上升,且在200 s左右达到最低;熔融层厚度随着环境温度的降低和风速的增大而逐渐减小,且最多减小25%。优化后的试样拉伸强度与室内标准焊接工艺的拉伸强度相差在5%以内,符合标准焊接质量要求。

PE管内穿插技术在城市铸铁燃气管网改造中的应用

文章以安徽省淮南市DN400铸铁燃气管道内穿插PE管道改造工程为例,针对城区老旧铸铁管网运行压力低、接口胶圈老化泄漏、市政道路大面积开挖改造不具备条件、用户众多且须不停输改造等实际问题,详细介绍了内穿插技术在铸铁燃气老旧管道改造工程中的施工方法、工艺技术关键控制要点及解决的实际技术问题,为下一步城镇铸铁燃气管道内穿插PE管道改造工艺工程提供了应用技术指导,也为老旧管网的系统改造提供了可行的参考解决方案。