静止平面应力裂纹尖端的静水应力相关理想塑性应力场

在裂纹尖端的应力分量都只是θ的函数的条件下,利用平衡方程和静水应力相关屈服条件,本文导出了静止平面应力裂纹尖端的静水应力相关理想塑性应力场的一般解析表达式.将这些一般解析表达式用于具体裂纹,我们就得到Ⅰ型和Ⅱ型裂纹尖端的静水应力相关理想塑性应力场的解析表达式.     

表面承受常静水载荷下弹性半无限体的表面稳定性分析

本文应用小变形叠加到大变形上的分析方法,考察了表面受常静水载荷作用下可压缩和不可压缩弹性半无限体的表面平面应变失稳问题,得到了各自的临界屈曲条件的一般形式.在此基础上.分别对由Blatz-Ko材料和谐和材料所组成的可压缩弹性半无限体以及由Mooney材料所组成的不可压缩弹性半无限体,详细讨论了表面所受的静水压力对临界屈曲条件的影响.     

Hydrostatic Extrusion of Poly(L-Lactide)

Poly-L-Lactide(PLLA) has been used as a bone fracture fixation material for several years. However, its mechanical properties are still not satisfied. To improve its mechanical properties, we examined the hydrostatic extrusion procedure on the PLLA rods made by Injection Molding process. The extrusion ratio was adjusted to 3, 6, 9, and 12. The molecular weight of the PLLA decreased from 260,000 to 200,000 after injection molding process, but it did not change during the hydrostatic extrusion procedure. The melting point of PLLA hydrostatic extrusion products were increased with the extrusion ratio, but the increment was not obviouse. Extrusion products having low extrusion ratio had α-form crystal in them, extrusion products having high extrusion ratio had both of α and β-form crystall in them. At extrusion temperature of 145°C, PLLA rods showed the best flowing trends in the pressure medium of PEG 400. Extrusion temperature is placed in the range of crystalline transition temperature and melting point of PLLA. At extrusion ratio 9∼12, the extrusion products showed the best mechanical properties. The highest bending strength of the extrusion product was over than 350MPa. It is far stronger than that of the human cortical bone (200MPa). SEM observations showed that the fiber structure began to appear at an extrusion ratio ER=3, and at the extrusion ratio ER=6, the chain axes of PLLA became aligned to the extrusion direction. The structure of extrusion products at the high extrusion ratio showed highly oriented fiber structure composed of micro-fibril. At high extrusion ratio tranformation from α-crystal to β-crystal was also observed.     

流体静高压原位磁测量的误差研究（三）——综合兼顾两种影响

 先后选用1至3片非晶Fe_46.3Co_0.03Ni_46.5Si_3.75V_0.92B_2.5合金薄带作样品,插入13层密绕直螺线管内,分别在高静水压容器内和其他四种不同环境中测量它们的磁化曲线、磁导率曲线和起始磁化曲线,再次研究了初级线圈采用多层直螺线管对铁镍合金样品的误差。（１）实验结果表明：既存在样品材料被磁化而形成的退磁场H',也存在漏磁通引起周围铁器磁化而形成的退磁场H'。（２）为了缩小H'的影响,只用1片非晶合金薄带作样品时,H'的影响变得严重,导致μ_m和μ_i出现惊人的误差：Δμ_m/μ_m=50%,Δμ_i/μ_i＝104%。（３）为了综合兼顾这两种影响,采用3片非晶合金薄带作样品时,虽然H'的影响增大一点,但是H'的影响被更多地削弱,所以环境磁化引起的误差反而减小：Δμ_m/μ_m=29%,Δμ_i/μ_i＝15.5%。     

An implicit numerical algorithm for solving non‐hydrostatic free‐surface flow problems

Details are given of the development of a two‐dimensional vertical numerical model for simulating unsteady free‐surface flows, using a non‐hydrostatic pressure distribution. In this model, the Reynolds equations and the kinematic free‐surface boundary condition are solved simultaneously, so that the water surface elevation can be integrated into the solution and solved for, together with the velocity and pressure fields. An efficient numerical algorithm has been developed, deploying implicit parameters similar to those used in the Crank–Nicholson method, and generating a block tri‐diagonal algebraic system of equations. The model has been applied to simulate a range of unsteady flow problems involving relatively strong vertical accelerations. The results show that the numerical algorithm described is able to produce accurate predictions and is also easy to apply. Copyright © 2001 John Wiley & Sons, Ltd.     

硬质聚氨酯泡沫力学特性的静水压力加载实验方法研究

泡沫材料在多轴载荷下的力学性能是工程中非常关心的问题。利用土壤的三轴压缩试验装置,通过试验方法的改进,提出了一种体应变测定和修正的方法,对硬质聚氨酯泡沫材料的静水压力特性进行了研究,得到了一些有价值的数据和结论。研究表明:在准静态静水压加载条件下,该材料的应力-应变曲线明显地分为弹性段、塑性段和压实段,且屈服强度比单向压缩时略大、压实应变略小。最后通过不同高度的试样对比试验,对聚氨酯泡沫材料的不均匀变形和弯曲的原因进行了分析和比较,指出了试验时应该注意的问题。     

棒材通过锥形模静液挤压成形的无网格法分析

建立了一种基于初始构形及有限变形的粘塑性弹性本构关系，并由空间描述的Galerkin能量弱变分原理，经一致转换得一整体拉格朗日方程描述下的动量平衡方程．同时经线性化处理给出了显示中心差分法求解格式，以棒材通过锥形模的静液挤压成形为例进行了全面的EFG法数值模拟，从而证明了有限变形粘塑性EFG法对实际成形工艺分析、优化及设计的有效性。     

深海静水压力环境下低合金高强度钢腐蚀行为研究

通过自行设计的深海环境模拟装置,采用静态挂片失重、动电位极化曲线及电化学阻抗谱（EIS）等方法系统研究了深海静水压力环境下低合金高强度钢（HSLA钢）在3.5% NaCl溶液中的腐蚀行为,并与常压下的结果对比,探讨了静水压力下HSLA钢在深海环境中的腐蚀行为. 结果显示,静水压力并没有改变HSLA钢在3.5% NaCl溶液中的腐蚀历程,不甚影响其阴极过程,而主要提高了其阳极腐蚀速率,这可能与高静水压下Cl-活性的增加有关.     

静压下Znse／Zn_（1－x）Cd_xSe应变超晶格的光致发光研究

本文首次在室温和０—２．５ＧＰａ静压范围内研究了Ｚｎｓｅ／Ｚｎ０．２６Ｃｄ０．２６Ｓｅ应变超晶格的静压光致发光，观察到了室温条件下的超晶格阱层的重空穴激子跃迁随压力的亚线性变化的特性．经过计算机拟合实验数据得到了一阶和二阶压力系数．理论计算得到的一阶压力系数与实验得到的压力系数符合得较好。     

Comparing analytical and numerical solution of nonlinear two and three‐dimensional hydrostatic flows

New test cases for frictionless, three‐dimensional hydrostatic flows have been derived from some known analytical solutions of the two‐dimensional shallow water equations. The flow domain is a paraboloid of revolution and the flow is determined by the initial conditions, the nonlinear advective terms, the Coriolis acceleration and by the hydrostatic pressure. Wetting and drying is also included. Some specific properties of the exact solutions are discussed under different hypothesis and relative importance of the forcing terms. These solutions are proposed for testing the stability, the accuracy and the efficiency of numerical models to be used for simulating environmental hydrostatic flows. The computed solutions obtained with a semi‐implicit finite difference—finite volume algorithm on unstructured grid are compared with the corresponding analytical solutions in both two and three space dimension. Excellent agreement are obtained for the velocity and for the resulting water surface elevation. Comparison of the computed inundation area also shows a good agreement with the analytical solution with degrading accuracy observed when the inundation area becomes relatively large and for long simulation time. Copyright © 2006 John Wiley & Sons, Ltd.