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It is clarified for the first time that the thermal fatigue failure of solder joint is actually a creep strain low cycle fatigue failure, and a physical model for creep fatigue crack propagation has been proposed. It was pointed out that creep strain increases in the high stress area ahead of the tip of thermal fatigue crack, results on one hand that the slide of crack tip increase, inactivation more serious and crack close length increases, the other hand, that intergranular crack exists, whose direction will affect the fatigue crack propagating.

本文首次阐明了焊点的热循环失效本质上是以焊点内循环蠕变为主要应变的低周疲劳失效，并在此基础上提出了蠕变疲劳裂纹扩展的物理模型，指出热循环裂纹前端的高应力区内，蠕变加剧，使裂纹前端滑移增加，裂纹钝化加剧，导致随后的裂纹闭合扩展长度增加；同时蠕变也使裂纹前端的高应力区出现晶间裂纹，蠕变沿晶裂纹对主裂纹扩展的影响取决于沿晶裂纹的连接方向。

The main research tasks and results are as follows:(1) Through comparing the stress intensity factor of compact tension specimen calculated by finite element software with the theoretical value, the feasibility of calculating fracture parameters of crack tip in ABAQUS software was verified.(2) The relationship between the elastic modulus of the material and research scale was studied based on deriving the cohesive stress theory and other relevant theories. And the elastic modulus of the material on meso-scale was determined.(3) Global model and sub-model of the finite element were built in th...e macro-scale, and stress-strain field nearby the crack tip was analyzed, and the results show that the detailed stress-strain in the crack tip could be obtained by using the sub-model technique.(4) In meso-scale, the crack growth model was also established by assuming the crack propagating along the grain boundary, and the detailed stress-strain field in the crack tip was obtained.(5) The effect of crack length on Von Mises stress, and maximum principal stress and strain was analyzed in meso-scale when equivalent KI equals 30MPa.m1/2. And the results show that except for crack tip area, the stress-strain distribution in whole specimen is not affected.

主要完成研究内容和取得成果如下：(1)利用有限元软件计算出紧凑拉伸试样的裂纹尖端应力强度因子KI值，其结果与理论值一致，从而验证了利用ABAQUS计算裂纹尖端相关断裂参量的可行性；(2)在研究内聚应力等相关理论的基础上，推导出了研究尺度与材料弹性模量的近似关系，并确定了介观尺度上的弹性模量；(3)在宏观尺度上建立了全局有限元计算模型和子模型，得到了裂纹尖端应力应变场分布，结果表明利用子模型技术获得比较准确的裂纹尖端应力应变场分布是可行的；(4)在介观尺度上利用平均晶粒尺度的方式建立了裂纹沿晶扩展模型，得到了裂纹尖端断裂过程区的微观应力应变场；(5)当应力强度因子为30MPa.m1/2时，分析了介观尺度上在裂纹沿晶扩展过程中裂纹长度对Mises应力、最大主应力和应变的影响，结果表明，裂纹扩展长度对试样整体应力应变分布影响不大，而对裂纹尖端区域有较大影响；(6)介。。。

In spatial domain, this irregular flow is characterized by a propagating band structure of strain localization. According to the discoverers, this phenomenon is named as Portevin-Le Chatelier effect.

这一现象在时域上表现为应力的锯齿形和局部应变的阶梯形发展，同时伴随着空间上可传播的变形局域化，被称为Portevin-Le Chatelier效应。

As the beam further propagation, self-reconstruction of the Bessel beam generated. The divergence of the self-reconstruction beam causes the beam intensity decreasing and the bright spot size increasing as the beam propagating.

当光束继续传播，贝塞尔光发生自重建(Self-reconstruction)，但重建的Bessel光将会发散，光强随着传播距离增大而迅速下降，且中心亮斑尺寸也迅速增大。

ABSTRACT The self-propagating combustion reaction in Ti-W-C system has been studied systematically for the first time.

本文首次对Ti-W-C体系的自蔓延高温合成反应进行了系统的研究。

The basic principle and technology of self-propagating high-temperature boriding-and-eutecticum have been preliminary discussed.

初步探讨了自蔓延高温渗硼共晶化的基本原理及具体工艺。

Reactive Ball Milling technology appeared after self-propagating phenomenon in the process of ball milling was discovered.

球磨过程中自蔓延现象的发现，促使了反应球磨技术的产生。

Technical use of international advanced materials synthesis of self-propagating high-temperature synthesis, major equipment from the United States, Germany, Japan, Taiwan and other countries and regions in the introduction.

技术上采用国际先进的材料合成方法自蔓延高温燃烧合成，主要设备从美国、德国、日本、台湾等国家和地区引进。

Self-propagating High-temperature Synthesis technology is a new subject, whose special advantages have attracted material scientists' attention.

自蔓延高温合成技术是一门新兴的学科，因其独特的优越性而备受材料科学家的关注。

In this paper, the processes and the affect factors of the reaction of Ti and C by mechanically induced self-propagating reaction are described in details.

在本论文中，Ti和C经机械诱发自蔓延反应过程和影响因素被详细地描述了。

Aquatic or marsh-growing fern allies; known to have existed since the Cenozoic; sometimes included in Lycopodiales.

生活于水中或湿地的蕨类；从新生代生存至今；有时归于石松目之中。

The engine was uprated from a 90hp Franklin to a 125hp Lycoming.

改良过的引擎是从90hp到125hp莱康明富兰克林。