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1. chinaXiv:202101.00030 [pdf]

多孔介质突变界面处两相可压缩流体界面连接条件

彭小龙; 王超文; 邓鹏; 朱苏阳
Subjects: Mine Engineering Technology >> Development Engineering of Oil and Gas Well

多孔介质间突变界面在油气藏开发中广泛存在。传统的渗流理论认为压力和达西速度在非连续界面处是连续的,我们在以往的研究对其进行了证伪。多孔介质物性突变界面为固定界面,本文在前期不可压缩流体的基础上,以气-水两相为例,考虑流体的压缩性,建立了这类突变界面处流体压力和渗流速度的连接条件。研究结果表明,在多孔介质固定的物性突变界面:(1)总体压力必然连续,但各相流体压力可以不连续;(2)总渗流速度相等,但各相流体的渗流速度可以不连续;(3)固定突变界面与移动突变界面的连接条件不同,不能用Rankine–Hugoniot条件描述;(4)根据突变界面的连接条件以及两相达西公式根据界面两端压力以及流体分布可计算出跨物性突变界面的各相流体的流速,跨物性的突变界面的流量应取上游值

submitted time 2021-01-06 Hits642Downloads371 Comment 0

2. chinaXiv:202012.00069 [pdf]

多孔介质中不互溶气-液两相驱替前缘的界面条件

彭小龙; 朱苏阳; 梁保升; 王超文; 邓鹏
Subjects: Mine Engineering Technology >> Development Engineering of Oil and Gas Well

气-液两相驱替在油气藏开发中广泛存在。传统的渗流理论认为压力和达西速度在非连续界面处是连续的,我们在以往的研究对其进行了证伪。本文在前期不可压缩流体的基础上,以气-水两相驱替为例,研究了多孔介质中移动的气-水突变界面处的压力和渗流速度的连接条件。研究结果表明,在气-水两相驱替界面处:(1)总体压连续,但流体压力可以不连续;(2)总体流速的分布可以不连续,但满足特定的函数关系;(3)流体各相渗流速度不连续。

submitted time 2020-12-25 Hits1156Downloads506 Comment 0

3. chinaXiv:202012.00059 [pdf]

Analysis of mechanical performances of cylindrical wall in 3D printing processes

刘轩廷; 孙博华
Subjects: Mechanics >> Applied Mechanics

In order to enhance the overall structural stability of 3D printed concrete wall, we propose a novel scheme to produce a wavy wall with curvature along its contour direction. To validate the idea of the scheme, a single wave wall is set as a cylindrical wall and its mechanical performances are analyzed. The mathematical 3D printing model of the wavy wall is formulated by the shell theory while taking into account of additional parameters of the printing processes, the model will be used to analyze the two failure mechanisms of the cylindrical wall: elastic buckling and plastic collapse. Compared with the results of Suiker’s straight wall, it is found that when the parameters were same, the stability of the cylindrical wall is more than twice of the rectangular wall. Our studies indicate that it’s a feasible scheme to improve the printed structural stability by increasing curvature.

submitted time 2020-12-18 Hits773Downloads445 Comment 0

4. chinaXiv:202012.00019 [pdf]

3D打印进程中曲率对直立墙结构力学的影响

刘轩廷; 孙博华
Subjects: Mechanics >> Applied Mechanics

对于打印墙结构往往因为稳定性而失效的问题,本文提出了采用直立波纹墙的方法,即适当增加墙体沿轮廓方向的曲率,以求提高打印墙稳定性.本文通过将波纹墙的单个波纹视为单胞进行研究,取曲率为常数,并进行结构闭合处理,以求稳定性最大化,即分析柱壳形直立墙在3D打印进程中的力学性能.此模型利用 Goldenveizer-Novozhilov壳体理论,加入打印进程参数,包括打印速率、打印材料固化特征、柱壳几何特征、以及自重作用影响,对圆柱壳的两种破坏机理:弹性屈曲和塑性破坏进行分析.利用Suiker[22] 首次提出的无量纲参数 (暂称Suiker数),对柱壳形直立墙弹性屈曲与塑性破坏间的竞争关系进行描述.将结果与文献[22]进行比较,发现当参数完全相同情况下,将柱壳形直立墙比矩形直墙结果对比发现,稳定性提升了两倍有余.同时给出了通过曲率的改变达到此类参数下柱壳结构稳定性最大化的方法,即通过拟合的手段,得到失效高度随曲率变化函数,据此对失效机制区域进行划分.这表明该模型可用于探讨打印进程中曲率对直墙结构的力学性能影响,并可通过调整参数对结构作出优化.同时,通过引入曲率,将直立墙沿轮廓方向打印成波纹墙,对于提高打印墙结构稳定性是一个简单可行的方案.

submitted time 2020-12-10 Hits2344Downloads618 Comment 0

5. chinaXiv:202010.00005 [pdf]

Caladine-English折板吸能器的能量吸收能力分析

孙博华; 陈品元
Subjects: Mechanics >> Solid Mechanics

本文在 Zhang-Yu工作的基础上, 对 Caladine-English 折板吸能器的能量吸收能力进行了细致分析. 我们利用 Maple软件对 Caladine-English折板吸能器的 Zhang-Yu吸能器方程编写了通用程序, 并首次求得了吸能器的广义坐标(转角)随时间的变化规律. 在此基础上, 对于不同参数变化对 Caladine-English折板吸能器的能量吸收能力的影响进行了比较研究, 其中为了刻画结构的吸能能力, 定义了吸能因子. 为了更好的了解吸能器的运动受参数变化的影响, 我们计算了吸能器动力学的相图. 经过大量的数值模拟, 发现从吸能能力上看, 4折板吸能器应当是``质量敏感''型吸能器,完全支持Zhang-Yu的结论: 即 Caladine-English折板吸能器是``质量敏感''型吸能器.

submitted time 2020-10-13 Hits2435Downloads624 Comment 0

6. chinaXiv:202008.00090 [pdf]

可乐易拉罐在轴-侧-扭-内压联合作用下的屈曲地貌

宋广凯; 孙博华
Subjects: Mechanics >> Applied Mechanics

本文利用非线性有限元分析程序 ABAQUS 研究了柱壳曲屈问题,并应用到了可乐易拉罐的曲屈分析。首先从数值模拟上验证了Virot 等学者的可乐易拉罐曲屈实验结果,然后为了获得曲屈的一些普适结果,进一步考察了柱壳的曲屈表现。对柱壳结构在不同荷载组合、不同几何参数作用下进行了细致的分析。为了讨论的直观,本文绘制了柱壳结构在受到侧压-轴压荷载作用下外力-曲屈荷载-位移三维地貌图(称为landscape)。结果表明:在侧压-轴压-扭转荷载作用下试件力-位移曲线出现了“cliff”(断崖)现象;扭转荷载的施加不利于试件整体稳定性,并造成了试件对初始缺陷的敏感性;对于受到轴压-扭转试件,本文定义承载力为零的平面为“sea level” (海平面) 来区分试件破坏模式;通过对不同边界条件的试件进行分析,发现试件两端固接可以有效地整加结构的承载能力,提高稳定性。对柱壳结构内部充气可以大幅度提升结构的承载能力和稳定性,减小对初始缺陷的敏感度。

submitted time 2020-08-25 Hits3716Downloads856 Comment 0

7. chinaXiv:201708.00174 [pdf]

Analytical solutions to single scattering of SH waves by a cylindrical fiber with radially gradient interphases

章俊; 刘炼; 曾龙海; 鲍家定
Subjects: Mechanics >> Basic Mechanics

In this work, analytical solutions to the single scattering of SH waves by a cylindrical fiber with two specific radially gradient interphase layers are supported based on the method proposed by P.A. Martin (Martin 2002, JASA). In the first case, 1) shear modulus μ(r)=e^2βrand the square of wave number, k^2 , is a linear function of 1/r, and 2) μ(r)=e^(-βr^2 ) and k^2 is a linear function of r^2. For example, analytical solutions to single scattering of SH waves by a Sic fiber with the above two interphase layers embedded in aluminum are presented. The calculated scattering cross sections are compared with values obtained from an approximate method (dividing the continuous varying layer into multiple homogeneous sub-layers). The two methods yield similar results. The contribution of this work benefits the validation of various numerical methods used in the inhomogeneous media.

submitted time 2017-08-08 Hits6353Downloads3809 Comment 0

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