液压支架关键部位数值模拟研究

利用数值模拟软件对液压支架整体受力情况进行研究,发现在顶梁偏载工况下与立柱接触的顶梁柱帽位置出现最大MISES应力值为608.8 MPa,最大位移为7.59 mm;而在顶梁扭转工况下顶梁上最大应力值为整机中的最大值,为750 MPa,最大的变形量为13.1 mm,同时通过对虚拟焊接下MISES应力值与一体化处理下焊缝应力值进行比较,确定了液压支架薄弱位置,为设备优化提供一定的保障。     

矿用液压支架掩护梁的受力分析及结构优化

掩护梁是液压支架重要的承力结构件,工作中容易因为受力过大而引发故障问题.以ZY4000型液压支架为例,开展了液压支架掩护梁结构的受力有限元分析研究,结果发现,掩护梁工作时存在显著的应力和位移变形集中现象,应力和位移变形最大值分别为858.89 MPa和18.812 mm.通过对应力和位移变形较大的部位增加厚度及较小部位减小厚度的方式,对掩护梁进行结构优化改进,优化后掩护梁的最大应力值降低到338.64 MPa,使其结构使用寿命提升了20％以上,对提高液压支架的作业安全性具有重要作用.     

矿用液压支架掩护梁的受力分析及结构优化

掩护梁是液压支架重要的承力结构件,工作中容易因为受力过大而引发故障问题.以ZY4000型液压支架为例,开展了液压支架掩护梁结构的受力有限元分析研究,结果发现,掩护梁工作时存在显著的应力和位移变形集中现象,应力和位移变形最大值分别为858.89 MPa和18.812 mm.通过对应力和位移变形较大的部位增加厚度及较小部位减小厚度的方式,对掩护梁进行结构优化改进,优化后掩护梁的最大应力值降低到338.64 MPa,使其结构使用寿命提升了20％以上,对提高液压支架的作业安全性具有重要作用.     

ZY13000/30/65型液压支架顶梁的强度分析与改进研究

以ZY13000/30/65型液压支架顶梁为研究对象,利用Solid Works建立三维模型,导入Workbench,根据标准给出的两种工况载荷,仿真液压支架在两种工况下应力分布情况,结合液压支架实际使用经验,对顶梁作出结构优化改进。仿真分析结果表明:优化后模型最大应力值为388 MPa,相较于原结构扭转工况最大应力459 MPa,减小71 MPa,对结构应力分布情具有良好的改善作用,结构优化有效地提高了顶梁的性能。     

关于ZP4000型液压支架顶梁在不同工况下的强度分析

以ZP4000型液压支架为研究对象,根据其工程图纸建立液压支架三维模型,设置好液压支架的材料属性,选择两种典型工况分析该型液压支架顶梁的强度分析结果.经计算分析得出,偏载工况最大应力为553.8 MPa,扭转工况最大应力值为509.9 MPa.并结合分析计算结果提出顶梁优化改进意见,以期对液压支架结构设计与优化提供理论参考.     

不同工况下ZF13000型矿用液压支架顶梁结构性能分析

以ZF13000型矿用液压支架中顶梁为分析对象,采用有限元分析方法,对顶梁在不同工况下的结构性能进行有限元仿真分析.分析认为:在两种工况下,顶梁的中部及柱窝等区域均出现了较大程度的应力集中及结构变形,是整个结构的薄弱部位.基于此,提出了顶梁结构优化改进的措施,这对提高顶梁及延长其液压支架的结构性能及使用寿命具有重要的指导意义.     

基于不同工况下的ZF12000型矿用液压支架顶梁结构强度分析

针对矿用液压支架中顶梁在使用过程中出现了结构变形、局部开裂等失效现象,以ZF12000型液压支架为例,在分析其顶梁结构特点基础上,通过三维建模和仿真建模,对顶梁在不同工况下结构强度进行仿真分析,结果显示,顶梁的柱窝及中部铰接耳部位为薄弱部位,需进行重点改进,因此提出了顶梁的结构改进措施,以提升顶梁结构性能.     

矿用液压支架顶梁的有限元分析及改进研究

基于矿用液压支架顶梁结构的特点,以ZY8650型掩护梁液压支架为研究对象,构建矿用液压支架顶梁带焊缝模型,采用罚函数法对模型进行接触处理,并对所构建的模型进行网格划分,开展具体模型分析计算。根据分析计算结果来看,带焊缝顶梁的实际应力和位移均大于无焊缝顶梁。在矿用液压支架顶梁设计中必须要对焊缝所造成的影响进行综合考虑,以此来降低矿用液压支架的使用风险。     

ZFS8000型矿用液压支架中顶梁结构分析

提高液压支架中顶梁的结构强度,是当前保证液压支架高效安全运行的关键因素.分析ZFS8000型矿用液压支架及顶梁的结构特点,采用有限元分析方法,分析顶梁在不同工况下的结构性能特点,得出顶梁的柱窝及中部筋板是整个结构的薄弱部位,重点从材料属性、结构尺寸、热处理等方面行了顶梁的结构优化改进,对提高顶梁的使用寿命及液压支架的工作安全具有重要意义.     

液压支架偏载工况下特性试验分析

以矿用液压支架原型试验为依据,选取常用的ZF15000/24/45型放顶煤支架和ZY12000/29/63型掩护式支架分别进行了支架在承受偏载工况下支护性能、压缩量、变形量等参数变动趋势规律的试验与分析.结果表明,在偏载工况下,液压支架初撑力是影响支架支护性能顺利发挥的关键性参数,且液压支架压缩量、顶梁变形量等均对顶板...     

Electron and light microscopy studies on the domain structures of Zn3B7O13Cl, Zn3B7O13Br and Zn3B7O13I ferroic boracites

The domain structures of Zn₃B₇O₁₃Cl, Zn₃B₇O₁₃Br and Zn₃B₇O₁₃I boracite single crystals were studied by means of polarized light in conjunction with electron microscopy. Single crystals of the three compositions were grown by chemical transport reactions in closed quartz ampoules, at a temperature of 900 °C and were examined by polarizing optical microscopy (PLM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For both PLM and SEM, the same as‐grown samples were used without having to resort to metallization of the crystal faces. For TEM the single crystals were crushed and mounted on holey carbon films. Comparative electron microscope images were useful for revealing the domain structure of these ferroelectric/ferroelastic materials previously observed between the crossed polars of an optical microscope. X‐ray diffraction analysis of the pulverized crystals was performed for this triad of halogen boracites containing zinc as a common metal.     

Cylindrical specimens for KIC of rocks

Stress intensity factors for pairs of diametrically opposite radial cracks on the inside of a jacketed pressurized hole in a thick cylinder have been calculated by using finite element technique. Burst tests on thick cylinder rock samples under above conditions have been performed and the K_IC values for Antrim Shale and Limestone determined. The method is very convenient for rocks whose samples are often available in form of cylindrical bars drawn as cores from underground drilling.     

GT/CAD/CAPP/PDM/ERP系统集成研究

研究ETO生产方式下以成组技术为基础的CAD/CAPP/PDM/ERP的集成方法,包括面向CAD/CAPP/PDM/ERP的集成的成组信息编码,基于成组编码的CAD/PDM集成、CAPP/PDM集成和PDM/ERP集成.提出了基于成组技术的CAD/CAPP/PDM/ERP集成框架,研究了贯穿于CAD、CAPP、PDM与ERP系统的统一的成组编码方案和信息编码方案.     

基于太赫兹光谱的人参和西洋参鉴别

为了快速区分人参和西洋参,依据两者所含的人参皂苷在太赫兹波段具有不同指纹光谱,提出了一种基于人参皂苷的太赫兹光谱鉴别人参和西洋参的方法。采用MATLAB软件识别人参和西洋参的太赫兹光谱,同时根据太赫兹光谱特征并通过标准的主成分分析(PCA)区分出人参、西洋参。实验结果表明,基于太赫兹光谱的主成分分析可精确区分出人参、西洋参,并且还可以应用于其他类似物质的区分中。     

Analysis of the Rk surface roughness parameter proposals

European manufacturers have proposed a set of surface roughness parameters based on an examination of the variation in slope of the bearing ratio curve of a surface profile. It is shown, that the proposed procedure provides no useful information, and indeed is misleading, since the bearing ratio curve of even a normally-distributed random surface profile exhibits the expected variation in slope when plotted on rectangular coordinates. On the other hand, the desired information is readily obtained by a similar examination of the cumulative height distribution of a surface profile (the unity complement of the bearing ratio) when it is plotted on normal probability coordinates.     

永磁同步电机积分滑模观测器控制

对永磁同步电机观测器控制进行研究,针对传统滑模观测器存在控制精度低、系统抖振较大的不足,设计了一种永磁同步电机积分滑模观测器控制。积分滑模控制具有控制精度高、系统抖振小的特点。积分滑模观测器可以有效提高电机控制精度,增强控制系统抗干扰能力。采用饱和函数代替符号函数进行滑模控制律设计,降低控制系统固有抖振,使滑模控制动态性能提高。通过仿真验证了积分滑模观测器控制策略的可行性。     

Characterization of cast Al86Mn3Be11 alloy

An Al₈₆Mn₃Be₁₁ alloy cast into copper mould was subjected to metallographic investigation. The as-cast microstructure consisted of a quasicrystalline icosahedral phase (i-phase), Be₄AlMn phase and, occasionally, a hexagonal phase. Al-rich solid solution represented the dominant phase. The chemical compositions of phases were determined using AES. The composition of the Be₄AlMn slightly deviated from the stoichiometric composition, whereas the composition of the i-phase was approximately Al₅₂Mn₁₈Be₃₀, containing an appreciable amount of Be. The average composition of the hexagonal phase was Al₆₆Mn₂₁Be₁₃. Deep etching and particle extraction provided a deep insight into the three-dimensional morphology of the i-phase and the hexagonal phase, whereas Be₄AlMn was slightly attacked by the etchant. The i-phase was present predominantly in the form of dendrites and a rodlike eutectic phase. The hexagonal phase was primarily in the form of hexagonal platelets, whereas Be₄AlMn was rather irregular in shape. The morphology of the i-phase can be explained by predominant growth in 3-fold directions and the lowest energy of the 5-fold planes, leading to the faceting and adopting a pentagonal dodecahedron shape. The brightnesses of phases in the backscattered electron images were rationalized by determining their backscattering coefficients. TEM investigation showed considerable phason strain in the i-phase, and the polycrystalline nature of the Be₄AlMn phase.     

Investigation on the impact behavior of Al2O3-SiC-MgO nanoceramic/metal laminated composite

Lightweight laminated composites containing a ceramic front layer and a metallic backing layer were used in order to protect people, moving equipment, and mobile vehicles from high velocity impact and the increased mobility of mobile vehicles. In this study, by adding10 vol% SiC and 500 ppm MgO nanoscale particles on the microstructure of Al ₂ O ₃ matrix and applying optimum sintering conditions, ceramic performance against high-speed projectile impact was improved. To perform this investigation, a number of target samples with two different types of front layers (alumina and Al ₂ O ₃-SiC-MgO nanocomposite ceramic) were produced. Impact tests were conducted on these samples using 7.62 mm projectiles with a velocity of 820 ± 15 m/s. The amount of bulge and bending of the backing layer caused by impact tests was measured. The results of the impact tests on the samples made of Al ₂ O ₃-SiC-MgO nanocomposite ceramics and alumina were also compared and analyzed. The results indicate that the substitution of Al ₂ O ₃-SiC-MgO ceramic layer — which is proffered in this paper — instead of pure alumina ceramic layer, decreases the areal-density of the samples by at least 30% and improves mechanical properties by about a 60% increase in flexural strength and 100% growth of the energy distribution factor, which impressively increases impact energy absorption.     

Electron microscopy of crack/particle interactions in Al2O3/SiC nanocomposites

Crack/particle interactions in alumina/silicon carbide nanocomposites have been investigated by scanning electron microscopy and transmission electron microscopy, with cracks induced by Vickers microindentation. Intergranular cracks are frequently deflected into grains by SiC particles on grain boundaries inclined to the average direction of crack propagation. This mechanism is proposed to explain the change in the fracture mode from intergranular fracture for monolithic alumina to predominantly transgranular fracture for the nanocomposites. Neither stress-induced microcracking around SiC particles nor significant crack deflection by intragranular particles was found to occur in the nanocomposites. It is argued that an addition of nanoparticles may not be a promising approach for increasing the toughness of alumina.     

Near-field second harmonic imaging of the c/a/c/a polydomain structure of epitaxial PbZrxTi1–xO3 thin films

Near-field optical second harmonic microscopy has been applied to imaging of the c/a/c/a polydomain structure of epitaxial PbZr _x Ti_{1– x} O₃ thin films in the 0 <  x  < 0.4 range. Comparison of the near-field optical images and the results of atomic force microscopy and X-ray diffraction studies show that an optical resolution of the order of 100 nm is achieved. Symmetry properties of the near-field second harmonic signal allow us to obtain good optical contrast between the local second harmonic generation in c- and a-domains. Experimentally measured near-field second harmonic images have been compared with the results of theoretical calculations. Good agreement between theory and experiment is demonstrated.