SOLUTION OF DIFFERENT HOLES SHAPE BORDERS OF FIBRE REINFORCED COMPOSITE PLATES BY INTEGRAL EQUATIONS

Accurate boundary conditions of composite material plates with different holes are founded to settle boundary condition problems of complex holes by conformal mapping method upon the nonhomogeneous anisotropic elastic and complex function theory. And then the two stress functions required were founded on Cauchy integral by boundary conditions. The final stress distributions of opening structure and the analytical solution on composite material plate with rectangle hole and wing manholes were achieved. The influences on hole-edge stress concentration factors are discussed under different loads and fiber direction cases, and then contrast calculates are carried through FEM.

Isogeometric Analysis and Shape Optimization of Holed Structures via the Patch Removing Technique

In this study,a patch removing based Isogeometric analysis(PR-IGA)method is proposed to conduct the holed structural analysis with only one parametric domain,in which there are also no trimmed elements.The theoretical foundation of this novel patch removing approach is that any holed structure can be obtained by removing sub-patches(i.e.,the holes)from an intact base patch.Since the parametric domains of these patches are all meshed by rectangular grids,the elements in the resulted holed structural parametric domain could all be untrimmed rectangles under certain mapping conditions.To achieve the special condition,a systematic technique consisting of T-spline local refinement and control points substitution/adjustment is provided.Due to the intactness of parametric elements,the analysis procedure of holed structures based on the proposed PRIGA is quite simplified and efficient compared to traditional multi-patch and trimming schemes.Moreover,after the deduction of analytical sensitivities related to structural mass and mechanical responses,the PR-IGA is directly employed in the holed structural shape optimization to successfully eliminate the need for model transformation during modeling,analysis and optimization processes.Numerical examples involving analysis and shape optimization of complex holed structures are presented to demonstrate the effectiveness of the proposed method.

INTEGRAL EQUATION METHOD'S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.

Data mining optimization of laidback fan-shaped hole to improve film cooling performance

To improve the cooling performance, shape optimization of a laidback fan-shaped film cooling hole was performed. Three geometric parameters, including hole length, lateral expansion angle and forward expansion angle, were selected as the design parameters. Numerical model of the film cooling system was established, validated, and used to generate 32 groups of training samples. Least square support vector machine(LS-SVM) was applied for surrogate model, and the optimal design parameters were determined by a kind of chaotic optimization algorithm. As hole length, lateral expansion angle and forward expansion angle are 90 mm, 20° and 5°, the area-averaged film cooling effectiveness can reach its maximum value in the design space. LS-SVM coupled with chaotic optimization algorithm is a promising scheme for the optimization of shaped film cooling holes.

Terahertz-dependent identification of simulated hole shapes in oil gas reservoirs

Detecting holes in oil–gas reservoirs is vital to the evaluation of reservoir potential. The main objective of this study is to demonstrate the feasibility of identifying general micro-hole shapes, including triangular, circular, and square shapes, in oil–gas reservoirs by adopting terahertz time-domain spectroscopy(THz-TDS). We evaluate the THz absorption responses of punched silicon(Si) wafers having micro-holes with sizes of 20 μm–500 μm. Principal component analysis(PCA) is used to establish a model between THz absorbance and hole shapes. The positions of samples in three-dimensional spaces for three principal components are used to determine the differences among diverse hole shapes and the homogeneity of similar shapes. In addition, a new Si wafer with the unknown hole shapes, including triangular, circular, and square, can be qualitatively identified by combining THz-TDS and PCA. Therefore, the combination of THz-TDS with mathematical statistical methods can serve as an effective approach to the rapid identification of micro-hole shapes in oil–gas reservoirs.

3D analysis of functionally graded material plates with complex shapes and various holes

In this paper, the basic formulae for the semi-analytical graded FEM on FGM members are derived. Since FGM parameters vary along three space coordinates, the parameters can be integrated in mechanical equations. Therefore with the parameters of a given FGM plate, problems of FGM plate under various conditions can be solved. The approach uses 1D discretization to obtain 3D solutions, which is proven to be an effective numerical method for the mechanical analyses of FGM structures. Examples of FGM plates with complex shapes and various holes are presented.

Thermoelectric field for a coated hole of arbitrary shape in a nonlinearly coupled thermoelectric material

We study the thermoelectric field for an electrically and thermally insulated coated hole of arbitrary shape embedded in an infinite nonlinearly coupled thermoelectric material subject to uniform remote electric current density and uniform remote energy flux.A conformal mapping function for the coating and matrix is introduced,which simultaneously maps the hole boundary and the coating-matrix interface onto two concentric circles in the image plane.Using analytic continuation,we derive a general solution in terms of two auxiliary functions.The general solution satisfies the insulating conditions along the hole boundary and all of the continuity conditions across the perfect coating-matrix interface.Once the two auxiliary functions have been obtained in the elementary-form,the four original analytic functions in the coating and matrix characterizing the thermoelectric fields are completely and explicitly determined.The design of a neutral coated circular hole that does not disturb the prescribed thermoelectric field in the thermoelectric matrix is achieved when the relative thickness parameter and the two mismatch parameters satisfy a simple condition.Finally,the neutrality of a coated circular thermoelectric inhomogeneity is also accomplished.

Analysis of Film Cooling Effectiveness on Shaped Hole and Antivortex Hole

Film cooling is introduction of a secondary fluid （coolant or injected fluid） at one or more discrete locations along a surface exposed to a high temperature environment to protect that surface not only in the immediate region of injection but also downstream region. This paper numerically investigated the film cooling effectiveness on two types of hole geometries which are cut-shaped hole and antivortex hole. The 3D computational geometries are modeled with a single 30 deg angled hole on a flat surface. The different blowing ratios of 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5,5 and k-Epsilon turbulence model are used in this study. A two dimensional distribution of film cooling effectiveness in the downstream region of the cooling hole is performed. A comparison of spanwise averaged effectiveness is also performed in the field starts from center point of hole to X/D=-30.

离心式高速玉米精量排种器T形槽型孔设计与试验

针对离心式高速玉米精量排种器双粒种子并排填充导致重播严重的问题,该研究提出利用型孔槽对称凸台结构降低玉米种子并排填充概率的方法,设计了一种T形槽型孔。通过构建充种阶段玉米种子的力学模型,并结合玉米种子的形状特征确定了T形槽型孔基本结构参数。借助EDEM离散元仿真软件,以型孔槽前端长度、型孔槽后端面倾斜角以及型孔槽底部倾斜角为因素,以合格指数、重播指数与漏播指数为评价指标,设计二次正交旋转回归组合仿真试验。仿真试验结果表明:在作业速度18 km/h条件下,型孔槽前端长度为9.31 mm,型孔槽后端面倾斜角为43.37°与型孔槽底部倾斜角为70.5°时,排种质量最优,排种合格指数、重播指数与漏播指数分别为94.03%、1.72%与4.25%。台架验证试验结果表明:作业速度为15 km/h时,T形槽型孔的合格指数最高为95.16%,在此作业速度下,排种器的重播指数为1.42%,漏播指数为3.42%,满足高速精量播种要求;作业速度在12~21 km/h内时,T形槽型孔的平均合格指数为94.77%,相较于矩形槽型孔提升了3.13个百分点,相较于蹄型槽型孔提升了1.80个百分点,T形槽型孔的平均重播指数为2.06%,相较于矩形槽型孔降低了3.41个百分点,相较于蹄型槽型孔降低了2.49个百分点。该研究可为离心式高速玉米精量排种器优化提供参考。

Hybrid RANS-LES of Shaped Hole Film Cooling on an Adiabatic Flat Plate at Low Reynolds Number

Hybrid RANS-LES methods offer a means of reducing computational cost and setup time to simulate transitional flows. Several methods are evaluated in ANSYS CFX, including Scale-Adaptive Simulation (SAS), Shielded Detached Eddy Simulation (SDES), Stress-Blended Eddy Simulation (SBES), and Zonal Large Eddy Simulation (ZLES), along with a no-model laminar simulation. Each is used to simulate an adiabatic flat plate film cooling experiment of a shaped hole at low Reynolds number. Adiabatic effectiveness is calculated for Blowing Ratio (BR) = 1.5 and Density Ratio (DR) = 1.5. The ZLES method and laminar simulation most accurately match experimental lateral-average adiabatic effectiveness along the streamwise direction from the trailing edge of the hole to 35 hole diameters downstream of the hole (X/D = 0 to X/D = 35), with RMS deviations of 5.1% and 4.2%, and maximum deviations of 8% and 11%, respectively. The accuracy of these models is attributed to the resolution of turbulent structures in not only the mixing region but in the upstream boundary layer as well, where the other methods utilize RANS and do not switch to LES.

不同成形方式对WE43镁合金组织和力学性能的影响

采用激光选区熔化成形(SLM)、铸造及挤压方式制备了WE43镁合金试样,通过维氏硬度计、密度测试计、光学显微镜、扫描电镜以及拉伸试验机等设备分析了不同制备方式下WE43镁合金的宏微观组织和力学性能变化规律;设计了基于指数函数的模型对不同成形方式的WE43应力–应变曲线进行统一拟合,为WE43材料未来增材、减材以及等材工艺复合制造复杂零件打下基础。结果表明,SLM成形WE43有明显的各向异性,铸态和挤压态不明显。SLM成形WE43镁合金的强度最高,抗拉强度达到313 MPa,是铸态的183%;挤压态WE43镁合金塑性最好,伸长率达到10.2%,是铸态的232%;此外,SLM态镁合金密度只有1.731 g/cm^(3),仅为挤压态的85.7%和铸态的95.2%。在断裂特性上,SLM态和挤压态为韧性断裂,而铸造态为脆性断裂。在内部存在20μm左右孔洞形缺陷的情况下,SLM成形镁合金依然具有最高的强度,主要原因是SLM成形WE43镁合金平均晶粒尺寸仅为2.6μm,基体内存在大量的稀土相沉淀以及纳米级亚稳相。由此可知,通过进一步的后处理方法焊合SLM态镁合金内部孔洞形缺陷后,材料力学性能可以大幅提高。

孔洞形状对层状岩石力学特性影响的FDEM数值模拟研究

为揭示孔洞形状对层状岩石力学性质和破坏模式的影响,采用有限元-离散元耦合数值模拟方法(FDEM)开展系列数值模拟研究。首先,阐述FDEM模拟层状岩石的基本原理,然后,开展不同层理倾角完整试样的单轴压缩模拟,并与试验结果进行对比验证。最后,对含有圆形、椭圆形、三角形、矩形和方形孔洞的层状岩石试样(β为0°、30°、45°、60°和90°)进行单轴压缩模拟研究。研究结果表明:对于不同孔洞形状的试样,抗压强度和试样破坏程度随层理倾角的增大呈V字型变化趋势,且均在层理倾角为0°时抗压强度取得最大值,在90°时破坏程度最为严重;孔洞的存在严重削弱了试样的力学性能,且削弱幅度与孔洞形状密切相关,其中方形和圆形孔洞对抗压强度的削弱能力最弱。将含不同形状孔洞试样的破坏模式随层理倾角的变化主要分为穿层理面拉剪混合破坏(β=0°)、沿层理面与穿层理面混合拉剪破坏(β=30°)、沿层理面剪切破坏(β=45°和60°)和沿层理面拉剪劈裂破坏(β=90°)。

异形孔电解加工流场仿真分析

针对航空发动机零部件中的花瓣状异形孔电解加工难题,文中建立了异形孔工件三维模型并抽取流道模型,对其进行流场仿真和优化。结合电场仿真计算,通过电流密度分布预测工件阳极型面的溶解差异,完成了阴极成型边界的修正。通过流场和电场分析,优化了通液孔的数量、大小和布局,以及阴极外形曲线,完成阴极结构设计。仿真结果表明:设置加工参数电解液入口压力为0.6 MPa,出口压力为0.1 MPa时,工件表面的电解液流速、压力以及加工区域工件边界的电流密度均具有良好的均匀性。

V形气膜孔气膜冷却效率的数值分析研究

采用数值模拟方法研究了不同角度和吹风比条件下V形气膜孔的气膜冷却效率,并与椭圆形气膜孔进行了对比。结果表明:相同吹风比下,3种V形气膜孔的冷却效率都要高于椭圆形气膜孔,角度对V形气膜孔冷却效率有较大影响。计算结果对目前涡轮叶片气膜孔的设计有一定指导意义。

高压涡轮导叶吸力面异型孔的对比研究

本文研究了高压涡轮导叶吸力面4种类型气膜孔在4组吹风比下的流动和换热特征,采用了数值模拟的方法获得了吸力面研究区域中4种气膜孔的绝热气膜冷却效率η、换热系数比hr/h0和净热通量减少量(NHFR),且分别进行对比分析。结果显示,簸箕孔因同时具有展向扩张角(β)增大冷气展向覆盖面积和流向扩张角(δ)提高射流贴壁性的优势,呈现出最大的绝热气膜冷却效率η和净热通量减少量(NHFR),但同时其增强了换热,使簸箕孔比其它3种气膜孔拥有最大的净热通量减少量(NHFR)的优势相较于其拥有最大的气膜冷效η的优势有所降低。而水滴孔相较于圆柱孔的优势不明显,故展向扩张角对气膜孔流动和换热特征的影响比流向扩张角大。

深孔聚能预裂爆破切顶卸压机理与应用

为解决悬顶导致的煤柱及邻近巷道高应力和大变形问题,结合工作面顶板地质条件,提出深孔聚能预裂爆破切顶卸压专项方案,采用数值模拟及现场试验对卸压效果开展综合研究。研究结果表明,煤层顶板在切顶后垂直应力减幅为21.62%,预裂切顶措施可显著降低煤柱及邻近巷道围岩应力水平。试验发现,炮孔内轴向贯穿裂缝明显,可实现采空区顶板及时垮落。顶底板在切顶后累计位移量减幅达59.27%,巷道两帮及顶底板移近变形得到有效控制,煤柱垂直应力增量显著降低。实践证明,采用深孔聚能预裂爆破切顶卸压效果显著,可大幅提高作业效率,为类似矿压防治工程提供借鉴。

双层壁涡轮叶片短径扇形气膜孔冷却性能数值研究

针对高冷效双层壁涡轮叶片表面应用短径扇形孔设计准则及强化气膜冷却,机理依旧不明的现状,本文利用流固弱耦合数值模拟技术研究了典型7-7-7和11-11-11扇形气膜孔应用于双层壁涡轮叶片设计的冷却特性。在宽范围吹风比下(0.6~2.4),比较了三种扇形气膜孔布置方案,包含叶片两侧同构布局7-7-7孔(简称SH1布局)和11-11-11孔(简称SH2布局)及新提出的异构布局(简称SH3布局),并以常规圆形孔作为比较依据。通过数值结果对比指出:在双层壁表面应用扇形孔代替圆形孔,最低可提升吸力面综合冷却效率17%,压力面7%。然而,扇形孔也会诱导两侧冷却性能差异扩大的现象。应用两侧孔型异构布局,要求在压力侧布置相较于吸力侧各向扩张角更大的扇形孔,可以有效改善叶片内部的流量配置,从而在提升综合冷却效率的基础上兼顾两侧温差缩小。在高吹风比条件下,上述异构诱发的冷却优势更为显著。但相对吸力侧、压力侧对扇形孔型结构参数的敏感性更大。因此,压力侧的异型孔气膜冷却挑战性更大。

“居行合一”——辽瓷盘口穿带瓶设计研究

辽瓷盘口穿带瓶设计的精髓在于其科学合理的功用契合了游牧迁徙的需求。基于翔实的历史文献资料与切身实地考察,从存蓄之易、提拎之利、握持之便、便携之需等主要功能视角切入,探求其设计优势与功用价值;并从游牧属性、科学理性、区域特性等鲜明的设计特色与制作技艺角度进行解读。以求在传承辽瓷盘口穿带瓶设计精髓的同时为现代设计艺术提供启迪与借鉴。

大断面隧道“楔形掏槽+高能孔”布设方法研究

在大断面隧道爆破中,由于掏槽孔的位置布置不合理,导致掌子面中间岩体时常出现“鼓肚”现象。为解决大断面隧道爆破“鼓肚”现象,提出了一种“楔形掏槽+高能孔”的炮孔布设新方法。以云南省鲁巧高速共和村隧道为工程背景,采用有限元软件LS-DYNA建立“楔形掏槽+高能孔”的数值模型,研究了炮孔底部有效应力和岩体动态损伤,并与现场隧道掏槽爆破方案进行对比,同时结合现场爆破试验对所提新方法进行验证。研究结果表明:现场实验验证了“楔形掏槽+高能孔”炮孔布设方法可有效消除“鼓肚”现象,减少掏槽孔和数码电子雷管数量,确定了该方法的合理性以及适用性;主掏槽孔底部测点1、2和3产生的应力值较小,当高能孔爆炸后,应力急剧上升至454.9 MPa,可对主掏槽孔爆破后遗留的中间保留岩体进行有效破除;采用改进后的爆破方法,掘进效率提升16.9%,炮孔平均利用率达到91.5%,炸药单耗降低19.7%。提出的大断面隧道“楔形掏槽+高能孔”布设方法在保障施工安全的同时,达到了降低成本提高施工效率的效果,为大断面隧道爆破方案优化设计提供借鉴。

金属矿山开采无切割井拉槽技术与应用

如何高效安全地形成切割拉槽是金属矿山开采过程中的关键环节。以典型铁矿山为工程背景,针对有切割井切割平巷拉槽法不能保证切割井施工爆破一次成井的问题,提出了以切割平巷为首爆自由面,利用多排扇形深孔逐次爆破,形成与上水平充分贯通切割立槽的无切割井拉槽法技术,并对该技术的施工方案、爆破方案和安全经济性进行分析。结果表明:扇形深孔炮孔梯形起爆顺序能减少爆破形成的碎块的抛掷作用,加强爆落岩石之间的碰撞挤压,提高了爆破破碎质量,为后续大量落矿创造条件;无切割井拉槽法较原有切割井切割平巷拉槽法,平均每爆落1 t矿石,节省炸药0.05 kg;无切割井拉槽法将切割巷道作为初始补偿空间,避免由于不同的岩石条件、穿孔误差及爆破操作等因素造成切割井无法一次成井的问题,提升了切割立槽的形成速度;可实现人员在巷道内装药,避免在采空区下作业带来的安全风险。无切割井拉槽法施工简单,成槽效果较好,实现了本质安全,为矿山降本增效提供了技术保证。