NUMERICAL SIMULATIONS OF WHOLE FIELD BEHAVIOR FOR ROUND BUOYANT JET

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An eight‐node hybrid‐stress solid‐shell element for geometric non‐linear analysis of elastic shells

This paper presents eight‐node solid‐shell elements for geometric non‐linear analysis of elastic shells. To subdue shear, trapezoidal and thickness locking, the assumed natural strain method and an ad hoc modified generalized laminate stiffness matrix are employed. A selectively reduced integrated element is formulated with its membrane and bending shear strain components taken to be constant and equal to the ones evaluated at the element centroid. With the generalized stresses arising from the modified generalized laminate stiffness matrix assumed to be independent from the ones obtained from the displacement, an extended Hellinger–Reissner functional can be derived. By choosing the assumed generalized stresses similar to the assumed stresses of a previous solid element, a hybrid‐stress solid‐shell element is formulated. Commonly employed geometric non‐linear homogeneous and laminated shell problems are attempted and our results are close to those of other state‐of‐the‐art elements. Moreover, the hybrid‐stress element converges more readily than the selectively reduced integrated element in all benchmark problems. Copyright © 2002 John Wiley & Sons, Ltd.     

A 3D contact smoothing method using Gregory patches

In this work, a method is developed for smoothing three‐dimensional contact surfaces. The method can be applied to both regular and irregular meshes. The algorithm employs Gregory patches to interpolate finite element nodes and provide tangent plane continuity between adjacent patches. The resulting surface interpolation is used to calculate gaps and contact forces, in a variationally consistent way, such that contact forces due to normal and frictional contact vary smoothly as slave nodes transition from one patch to the next. This eliminates the ‘chatter’ which typically occurs in a standard contact algorithm when a slave node is situated near a master facet edge. The elimination of this chatter provides a significant improvement in convergence behaviour, which is illustrated by a number of numerical examples. Furthermore, smoothed surfaces also provide a more accurate representation of the actual surface, such that resulting stresses and forces can be more accurately computed with coarse meshes in many problems. This fact is also demonstrated by the numerical examples. Published in 2002 by John Wiley & Sons, Ltd.     

各向加权异性有限元法在不可压粘性流动计算中的应用

本文利用各向异性张力有限单元，考虑到其独特的性质，提出了一种各向加权异性的算法，即在不同方向采用不同连续性的插值函数，然后再在原连续性较弱的方向以连续性较强的插值函数计算，最后把两次计算的结果加权处理。这种方法可以适应两个方向连续性要求不同或相同的各种情况，即克服了一般各向异性张力有限单元的局限性，又大大减少了存贮量和计算量。     

The effect of particle distribution on damage formation in particulate reinforced metal matrix composites deformed in compression

Image analysis results are reported on the generation of damage in particulate reinforced metal matrix composites during compressive deformation. The technique allows the automated collection of data on the incidence of particle fracture and void formation in the matrix as a function of important microstructural parameters such as local particle volume fraction and particle size. There is a strong relationship between damage and the local volume fraction of the reinforcement proving that damage formation is accentuated in regions of particle clustering. With the SiC reinforced materials examined, there was observed to be a change in dominance of damage mechanism from particle fracture at low local volume fractions to void formation in the matrix within strongly clustered regions. The results are compared with finite element (FE) modelling of the compressive deformation of clustered particles using a simple cluster of equi-spaced particles. The FE results suggest that plastic flow is generally inhibited in clustered regions. In certain highly clustered configurations shielding is such that flow does not occur in the heart of the cluster even at high levels of average plastic strain. The modelling suggests that the change in dominance of damage mechanism is related to the dramatic increase in tensile hydrostatic stresses in the matrix with higher levels of particle clustering.     

煤矿许用毫秒延期电雷管研究

文中对影响煤矿许用毫秒延期电雷管沼气安全性与延期时间精度的因素进行了研究。应用正交设计研制了新的延期药配方，确定了合理的雷管结构及装配工艺参数，产品性能达到ＧＢ８０３１《工业电雷管》的规定。     

A semi-analytic boundary element method for parabolic problems

A new semi-analytic solution method is proposed for solving linear parabolic problems using the boundary element method. This method constructs a solution as an eigenfunction expansion using separation of variables. The eigenfunctions are determined using the dual reciprocity boundary element method. This separation of variables-dual reciprocity method (SOV-DRM) allows a solution to be determined without requiring either time-stepping or domain discretisation. The accuracy and computational efficiency of the SOV-DRM is found to improve as time increases. These properties make the SOV-DRM an attractive technique for solving parabolic problems.     

通过室内实验及同位素测井技术评价高分子聚合物驱油效果

2500万超高分聚合物室内驱油实验研究了聚合物分子量、浓度、粘度、聚用量、段塞组合等各项性能指标对驱油效果的影响。本文根据室内实验结果,在北一区断西注聚后期开展矿场试验,取得了较好的开发效果。试验前后对比,注入粘度明显增大,月含水上升速度得到有效控制,吸入剖面有了新的动用,有63.1%的油井出现了明显的二次受效特征,取得了显著的经济效益。同时对驱油效果进行系统分析。驱油效果表明:应用2500万超高分聚合物是进一步提高聚驱采收率的有效途径。     

FE Simulation for Internal Inversion of Aluminium Alloy Tube

1 Introduction A double-walled invertube is difficult to fabricate other than applying inversion process. Such kind of invertube can be used as impact energy absorbing element in transport vehicles, like aircrafts and automobiles. Reddy T Y[1] did the analysis of Internal inversion and calculated the inversion load. Reid[2] et al. examined nosing and internal inversion of cold drawn steel tube by the finite element package ABAQUS. Recently, Rosa P A[3] et al. investigated Internal invers…