低渗透各向异性地层合理井排距比研究

以长庆油田某区块为例,从低渗透油藏流体地下渗流机理出发,根据低渗透油田开发地质特征,建立了102个不同的地质模型.通过102种方案的设计,在相应的地质模型基础上,运用数值模拟方法,对合理井排距比进行了研究,得到确定低渗透油藏合理井排距比理论图版,利用图版可以确定对低渗透油田不同各向异性程度下合理井排距比,低渗透油藏的经济有效地开发具有重要的理论意义和实用价值.     

有效修正ADI-FDTD算法中数值色散的一种方法

针对变换方向隐式(ADI)时域有限差分(FDTD)算法提出了一种改进方法,通过添加各向异性参数来修正相速度误差,从而减少数值色散,提高计算精度.给出了改进后的ADI-FDTD计算公式,并对改进算法的稳定性、色散关系以及各向异性参数的选取进行了研究,数值结果证明了所给方法的有效性.     

A simplified analysis of the effect of microstructure gradient on the stress relief of aluminum plates and extrusions

Many bulk forms of metal products are quenched after heat treatment in order to preserve material characteristics. Rapid quenching results in large thermal stress gradients that lead to high levels of residual stress. For products such as plates and extrusions, stretching by a few percent can reduce these stresses, but the stresses are not completely relieved. This report presents a simplified analytical model of the stress relief process illustrating the effects of through-thickness property gradients on residual stress after stretching. The basic conclusion is that for plates with uniform yield surface shapes through the thickness, the through-thickness residual stress range after stress relief is equal to the strength range in the direction of stretch. In extrusions, the bow after stress relief is proportional to this strength range. Cases are also considered in which the yield surface shapes range from isotropic to anisotropic through the thickness. Plastic anisotropy can perturb the effect of strength range on residual stress.     

超声马达各向异性摩擦材料性能的试验研究

根据超声马达对摩擦材料切向和纵向性能的不同要求,采用在酚醛树脂胶中添加玻璃丝布和玻璃纤维增强的方法制备出不同弹性模量匹配的各向异性摩擦材料,并对其性能进行了测试。结果表明:当摩擦材料垂直方向与水平方向的弹性模量的比值为0.71~1.42时,摩擦材料受振动头的正压力和驱动力先增大后减小,比值为1.24时,马达的正压力和驱动力最大,驱动效果最好。     

Effect of geometry and green density on the anisotropic sintering shrinkage of axisymmetric iron parts

Sintering shrinkage of prior cold compacted iron rings with different geometry (height to wall thickness ratio) and green density in the 6.5–7.3?g/cm³ range was investigated. It displays a minimum at an intermediate green density. Axial, tangential and radial shrinkages are different, due to the gradients of green density along the axial and the radial directions. Therefore, the effect of height on shrinkage and its anisotropy is the result of their effect on the stress distribution in the green parts during cold compaction, and the resulting green density and deformation experienced by the powder. Anisotropy decreases on increasing shrinkage.     

Measuring magnetic anisotropy with a rotatable ac electromagnet

Magnetic anisotropy of magnetic thin films was determined from a series of hysteresis loops measured via a rotatable alternate current (ac) electromagnet, the rotation angle of which could be continuously tuned at 360° with a high resolution. Co₂FeAl Heusler alloy films grown by molecular beam epitaxy were used to show the benefits of the method for measuring magnetic anisotropy.     

利用测井资料分析计算东海平湖油气田地应力

利用测井资料研究平湖油气田的地应力,对平湖油气田低渗透储层压裂、钻井和开发都有重要意义。文中利用密度、自然伽马、交叉偶极横波测井等资料,对平湖油气田地层的岩石力学参数(泊松比、弹性模量、体积模量、剪切模量、抗压强度、抗剪强度和抗张强度)进行了计算;为确定地层压力和构造应力系数,借鉴前人的研究成果,分别应用黄氏和葛氏地应力计算模型,建立平湖油气田地应力计算方法,并通过岩心差应变法地应力实验验证了该方法的准确性;采用基于XMAC-Ⅱ快横波方位法确定的平湖油气田的地应力方向,与岩心波速各向异性法及黏滞剩磁法地应力实验确定的地应力方向吻合较好。     

Anisotropic elasto-plastic solutions for cavity expansion problem in saturated soil mass

On the basis of the yield criterion of Matsuoka and Nakai (1974), novel elasto-plastic solutions are obtained for the cavity expansion problem in an anisotropic medium. The solutions are formulated by employing a small-strain analysis in an elastic zone and a large-strain analysis in a plastic zone around the cavity in a soil mass. In light of the initial condition, the plastic radius and the stress in the plastic zone are derived by incorporating the large-strain analysis, the influence of stress anisotropy (K0) and the non-associated flow rule, and two fundamental solutions for the cavity expansion problem under undrained and drained conditions are presented in an anisotropic soil mass. Finally, a comparison with the previous results is performed for verification.     

Temperature dependent coercivity of randomly assembled acicular Fe3O4 particles

Abstract

The Stoner‐Wohlfarth model and the chain‐of‐spheres fanning model are used to calculate temperature dependence of the coercivity of acicular single‐domain particles by taking thermal effect into consideration. Coercivity of the particles is evaluated by summing up the contributions of shape anisotropy, magnetocrystalline anisotropy and magnetostrictive anisotropy. The coercivities of randomly assembled Fe₃O₄ particles above the transition point (119°K) and below room temperature are calculated and compared with the published experimental data.