Intensity of Singular Stress Field at the Notch Tip of a V-Notched Bar

In this study, generalized stress intensity factors K_ and K_ are calculated for a V-shaped notched round bar under tension using the singular integral equation of the body force method. The body force method is used to formulate the problems as a system of singular integral equations with Cauchy-type or logarithmic-type singularities, where the unknown functions are the densities of body forces distributed in an infinite body. In order to analyze the problems accurately, the unknown functions are expressed as piecewise smooth functions using two types of fundamental densities and power series, where the fundamental densities are chosen to represent the symmetric stress singularity of 1/r^ and the skew-symmetric stress singularity of 1/r^. Then, generalized stress intensity factors at the notch tip are systematically calculated for various shapes of V-shaped notches

Evaluation of Static Strength by the Application of Mixed Mode Stress Intensity of Angular Corner

In this paper, a method of evaluation of static strength by the application of mixed mode stress intensity factors of angular corner is considered. Recently, it has been found that the stress field near a corner of jointed dissimilar materials is expressed as a sum of the symmetric state with a singularity of 1/γ^ and the skew symmetric state with a stress singularity of 1/γ^. In this respect, the fracture tests are carried out on the plane specimens of acrylic resin having a single sharp notch. Different artificial notches are introduced into the specimens with varying the opening and inclination angles. The fracture criterion for different shaped notch is discussed on the basis of the stress distribution near the notch. The usefullness of K_ and K_ for the evaluation of static strength under mixed mode fracture is confirmed through the experiment

Evaluation of Static Strength by the Application of Stress Intensity of Angular Corner

In this paper, a method of evaluating static strength by applying the newly difined stress intensity factor of an angular corner is considered. Recently, it has been found that the stress field near a corner of jointed dissimilar materials is expressed as a sum of the symmetric state with a singularity of 1/r^ and the skew symmetric state with a stress singularity of 1/r^ In this respect, the fracture tests are carried out on the plane specimens of acrylic resin having single and double sharp notches. Different artificial notches are introduced into the specimens with varying the opening angle, the notch depth, and the loading conditions. It is found that the fracture toughness K_ is almost constant independent of the notch depth and the loading condition. In addition, the value of K_ increases with increasing opening angle because of the decrease of the order of singularity. The fracture criterion for different opening angles of the notch is also discussed on the basis of the stress distribution near the notch. The usefulness of K_ in the evaluation of static strength is confirmed through experimentation

Design and Performance of Honeycomb Structure for Nanobubbles Generating Apparatus

In recent years, nanobubbletechnology has drawn great attention due to their wide applications in many fields of science and technology, such as water treatment, biomedical engineering, and nanomaterials. Nanobubble technology is also used for seafood long term storage. The nitrogen nanobubble water circulation can be used to reduce the oxygen in water and slow the progressions of oxidation and spoilage. In previous study, a kind of honeycomb structure for high efficiency nanobubble generation has been investigated. In addition, thesmall-scale honeycomb structure is designed for the broader applications. Comparing with stainless steel, acrylic resin and titanium have good corrosion resisting property in various liquids including the sea water. Therefore, acrylic resin and titanium are considered in this study. In this paper, the honeycomb structure is optimized and improved. Combining experimental solutions and CFD analyses, the performance of the generator is studied. The strength of the honeycomb structure is also analyzed by FEM. The relationship between nanobubble generation efficiency and structure type is discussed

植物模式标本的考证与数字化:以中国国家植物标本馆为例

模式标本是最重要的植物标本,是确定植物学名的依据,是植物分类学家从事植物系统分类研究必不可少的科学材料,也是开展专科专属研究、编写国家或地方植物志、进行植物区系调查研究、开发利用和保护植物资源的重要基本资料。但模式标本的人为和自然毁损难以避免,模式标本及其标签信息的数字化使得模式标本的形态、地理分布、采集等主要信息得到最大限度的永久保存,可以极大地方便模式标本信息的共享,可以为科学研究人员或相关人员提供植物形态、地理分布、历史变迁等多方面的信息。本文以中国科学院植物研究所国家植物标本馆维管束植物模式标本数字化建设为例,详细介绍了规范化整理模式标本的方法、模式标本数字化的操作流程,并通过大量实例介绍了模式标本考订的过程、常见问题的处理方法等,以期为其他单位开展模式标本数字化建设提供经验