Crack redirection with thermal secondary loading

In the current paper crack redirection due to a strategic placing of a heat source in the vicinity of a crack tip is studied. Analysis suggests that for PMMA and considered temperature range the only factor responsible for the deviation of crack trajectory is thermal stress. The simulation of crack growth in PMMA under external tension and secondary heat loading shows that a moving heat source in the vicinity of a crack tip can serve as a pointer for the crack trajectory. In highly conductive materials, redirection can be possibly effected with low-power thermal dipoles.     

断口分形研究与应用

采用经典的Ｍａｎｄｅｌｂｒｏｔ分形模型、Ｕｎｄｅｒｗｏｏｄ修正分形模型和分维谱模型对三种球墨铸铁断口的分形特性进行了研究，并应用于铸态铁拉伸断口的断 断裂机制分析。     

Issues in modelling of advanced heterogeneous ceramics

Summary The conceptual and computational issues regarding the development of models to predict microstructure/mechanical-property relationships in advanced ceramics are discussed. Advanced ceramics provide a particular challenge because their higher toughness or reliability, relative to monolithic ceramics, is a result of stable, distributed damage evolution. Capturing the details of distributed damage at atomistic and microstructural length scales is computationally prohibitive, but only in certain systems does it appear plausible to neglect atomistic and crack-tip details in favor of larger-scale damage propagation and interaction. Examples, mainly from the author's own work, are briefly presented to indicate the range of problems that have been addressed and the relative successes and failures.     

加气混凝土断裂能的测定及其分形几何的分析

根根RILEM推荐的带缺口的棱柱体试件劈裂的方法,测定了加气混凝土的断裂能,并计算了其比断裂能;测定断裂能的同时,也测定了裂纹过程区。分形几何理论计算的比断裂能,与实测值相一致。     

液化气球罐焊缝H2S应力腐蚀裂纹的返修补焊

对宁夏炼油厂一台200m3低合金钢球罐H2S应力腐蚀裂纹采用气刨打磨后补焊的返修方法表明，碳弧气刨时的骤热不会使裂纹向纵深扩展，只是必须在补焊前将返修部位焊缝两侧各100mm范围内打磨至完全露出金属光泽，以便彻底消除裂纹源，避免补焊时再产生新的微小裂纹。若返修深度不大于罐壁厚度的二分之一，则不必进行射线探伤检查，只须进行100％的超声波检查，在水压试验前后对返修部位进行100％磁粉探伤则是非常必要的。     

Expert system approach for reactor vessel integrity

This paper describes the development strategy of a prototype expert system, called RViES, for the reactor vessel integrity. The main objectives of the system are to assist engineers to perform fatigue and fracture mechanics analyses of reactor vessels quickly and accurately. The system consists of three parts; user interface, knowledge base and inference engine. Various rules recommended in codes and standards are stored in the knowledge base. Several case studies were performed to check the usefulness of the system.     

Fracture mechanics global approach concepts applied to creep slow crack growth in a medium density polyethylene (MDPE)

Creep fracture by slow crack growth is studied in a medium density polyethylene at 60 °C and 80 °C. Whereas elastic-plastic fracture mechanics load parameters fail to provide a unique temperature-independent correlation, that of the fracture mechanics for creeping solids C^∗ is proved to be relevant since this parameter correlates very well with the time to failure. Correlation established on both full notched creep tensile and double edge notched tensile tests was validated on cracked gas-pipe samples tested under hydrostatic pressure, extending the use of time to failure versus C^∗ diagram to predict lifetime of engineering components.     

用PIXE方法研究骨折家兔骨骼微量元素的变化

用质子激发X荧光分析法测定48只家兔在挠骨骨折愈合过程中骨骼中多种微量元素含量的变化。结果表明，Fe和Sr分别呈鼓凸形和下凹形规律性变化，故Fe和Sr含量的变化可作为骨折愈合过程的指示剂。在骨折愈合过程中发现骨骼和血液中元素钙的相对含量保持不变，故无法为西医用补充钙来治疗骨折的疗法提供依据，但我们的研究结果却表明中医补充微量元素治疗骨折的疗法是有道理的。     

基于灰色神经网络的骨折愈合应力预测

在骨折愈合应力准确预测问题的研究中,骨折愈合受许多因素的影响,应力是主要因素之一。为了加快骨折愈合的速度和提高质量,及时了解骨折愈合过程中应力的变化趋势并调整加力的大小,就显得很重要。然而应力的变化是不确定的,用传统的观察法医生很难确定次日应力的大小,用单一的GM(1,1)模型预测精度也不高。根据神经网络能有效修正灰色预测模型的思路,提出了基于灰色系统理论及径向基神经网络的组合预测模型。先用灰色系统理论中的GM(1,1)模型,用已有的实测应力数据对次日的骨折断面应力进行预测,然后用实测值与预测值的差值训练神经网络,从而可以对灰色预测的值进行修正。实验结果表明:提出的应力预测的模型获得较高的预测精度,说明组合预测模型效果优于单一的灰色预测模型。