双边切口薄板小试件动态弹塑性有限元分析

对［１］中采用的双边切口薄板小试件进行了动态弹塑性有限元分析，计算了动态积分，研究论证了积分作为该试验系统试件裂端表征参量的可行性；对深裂纹Ｒｉｃｅ公式计算动态积分的有效性进行了验证。为文［１］提出的平面应力型动态弹塑性起裂韧度的表征与测试方法提供了进一步的论证。     

三维压电弹性体断裂分析的基本解

求解了在材料的特征方程有重根时，三维压电弹性体的单位集中不连续位移和不连续电势基本解。讨论了重根对断裂力学问题解的影响。     

Effect of secondary zone dimensions on melt fracture manifestations of high density polyethylene

An experimental study was performed on melt fracture phenomena in extrusion of high density polyethylene. The purpose of the work was to study the sensitivity of melt fracture driven roughness to the size of recirculation zones, viz. secondary zones. The experimental apparatus consists of a right angle die and a hypodermic needle used as a capillary. The position of the needle relative to the die was adjusted using a special fixture. The roughness of the extrudate was studied as a function of penetration depth. A developed procedure provides a comparison between profile lengths of extruded strands. The computed mean, median, and mode values for roughness were presented as a function of capillary position. A qualitative analysis was conducted for the force oscillations during extrusion with a separate set of dies, equipped with the fixed capillaries of identical lengths and different depths of penetration. It was observed that the oscillatory pattern is sensitive to the sizes of the secondary zones. This qualitative observation supports the conclusions from the quantitative analysis that the roughness of the extrudate can be controlled through an adjustment of the secondary zone sizes.Partly presented at the 58th Annual Meeting of the Society of Rheology, Tulsa, Oklahoma, October 20–23, 1986     

用CT试样测定动态断裂韧性K_(1D)

在断裂冲击试验机上,用CT试样测定了35CrMnSiA、PCrN_(i1) M_0与45号钢的动态断裂韧性K_(1D),并与静态下的K_(1C)作了比较。K_(1D)一般比K_(1C)值低。本试验用瞬志波形存贮器寄存波形信号,用微机自动进行数据处理,并打印结果及绘制P—t曲线。     

Evaluation of fracture behavior of iron aluminides

Comparative fracture tests of three Fe-28%Al iron aluminides showed that alloys with Zr and C addition (FA-187) or with B, Zr, and C addition (FA-189) are extrinsically more susceptible to environmental embrittlement than the base ternary alloy (FA-186) under constant tensile loading condition. This may be caused by the variations of grain boundary morphology (i.e. changes of grain size and grain boundary cohesive strength) caused by the alloy addition. The effect of grain boundary size and cohesive strength are further investigated with reference to the susceptibility of hydrogen embrittlement. Finite element simulation of initial intergranular fracture of two iron aluminides (FA-186 and FA-189) are made. The computational scheme involves coupling the stress and mass diffusion analyses to determine crack-tip stress state and the crack tip hydrogen diffusion. Maximum strain failure criteria was adopted to simulate intergranular fracture. The numerical modeling results correlated well with the experimental data. The result further confirmed that the grain boundary morphology is important as it appears to control the intrinsic and extrinsic fracture behavior of iron aluminides.     

Self-affine cracks in a brittle porous material

Fractal mechanics and probabilistic methods are applied to an ideal porous material (gypsum rock). The behavior of the material fracture is brittle in essence, concluding that the lines of fracture propagation have self-affine invariance, due to the high rugosity of the crack developed within a wide but limited length interval of scale in the cracks. The validity of the mechanic equations of self-affine cracks are verified by a comparison between the predictions of self-affine fracture mechanics and the results of standardized mechanical tests, obtaining the fractal fracture toughness of gypsum rock.     

动态裂纹扩展中的裂纹滞留现象

借助于Ｊ．Ｒ．Ｗｉｌｉｓ等（１９９５）的动态权函数和Ｒｉｃｅ等（１９９４）的模拟方法，本文研究了裂纹前方开始环绕和穿透介质中各种粗糙微粒而形成粗糙的裂纹表面等非稳定现象．数值结果表明：在Ⅰ型情形，振荡性裂纹前缘运动源于应力强度波的建设性—破坏性相互作用．这些波包括膨胀波、剪切波和瑞利波系，彼此相互干涉且与裂纹运动边界相互作用，导致了裂纹前方扩展路径和扩展速度的连续波动．     

切口曲率半径对岩石断裂韧度KIC值的影响

本文对岩石三点弯曲试样的切口曲率半径与其断裂韧度 K_(Ic)值间的关系进行了详细的实验研究及理论分析.对岩石 K_(Ic)测试中切口的选择提出了建议方法.     

断裂力学的半解析相似边界元法

本文首先对弹性力学的相似边界元法进行了研究，推导了相应的计算公式。与传统的边界元法相比，相似边界元法由于只需在少数单元上进行数值积分，大大减少了计算量。在此基础上，对断裂力学问题，利用裂纹尖端位移场的解析表达式将裂纹尖端节点未知量转化为几个待定常数，提出了半解析相似边界元法，可大大减少最终形成的线性代数方程组的系数矩阵的阶数，进一步减小计算量。最后给出了算例，说明了本文方法的有效性。     

基于非协调元特征法的奇异性问题分析

提出了一个基于位移的、分析平面尖劈尖端奇性应力场和位移场问题的非协调FE特征分析法．该方法与过去原有求解裂纹尖端近似场的有限元特征分析方法导出公式的出发点不同，并且采用的单元形式为非协调元，尖劈尖端邻域内的位移场假定没有采用奇异变换技术，运用该方法处理了若干尖劈和接头的算例，所有的计算结果表明，该方法较原有方法使用的单元少而且精度高，具有应用广泛性。