SiC陶瓷与TiAl基合金扩散连接接头的强度及断裂路径

进行了SiC陶瓷与TiAl基会金（TAD）的真空扩散连接，给出了接头的剪切强度，并采用SEM、EPMA和XRD分析了接头的断裂路径。结果表明，在1573K和0．3～28．8ks的连接条件下，当连接时间较短时接头强度较高，如室温时为240MPa，高温（973K）时为230MPa，接头在（Ti5Si3CX＋TiC）／TAD界面处断裂。随着连接时间的增加，接头强度降低，接头的断裂路径也由靠近TAD的（Ti5Si3CX＋TiC）／TAD界面转向靠近SiC的TiC层内。

B/Al单向铺层复合板的力学性能及断裂行为的研究

研究了热压扩散结合工艺对B／Al复合材料的强度的影响，并对试样拉伸断口及断裂路径进行了研究。分析表明，试样断口有三种断裂模型，断裂路径同热压工艺有密切的关系。

基于3D-ILC含水平内裂纹脆性固体三点弯断裂特性研究

断裂力学是固体力学的重要分支,三点弯试验是力学领域的一个经典试验,含裂纹的三点弯研究多集中于穿透或表面裂纹,含纯封闭内裂纹的三点弯断裂研究较少。基于3D-ILC技术,在对试样表面无任何影响的情况下,生成任意参数的纯封闭内裂纹,开展含不同深度共勉内裂纹试样及完整试样三点弯断裂试验,分析应力双折射规律、破坏荷载、断口特征、断口特征区尺寸及破坏形态。通过对含不同深度内裂纹的试样进行数值模拟,得到裂纹尖端KⅠ、KⅡ、KⅢ分布规律。结果表明:(1)内裂纹改变了完整试样的应力双折射规律,云纹在裂纹上端呈半圆状,色差对比显著。(2)内裂纹的存在显著降低了试样三点弯破坏荷载,含深度10、20、30 mm单内裂纹试样及含深度20 mm双、三内裂纹试样与完整试样破坏荷载相比,下降百分比分别为11.8%、19.5%、78.4%、30.9%、35.5%。(3)内裂纹深度10、20mm试样与完整试样破坏形态均为动态裂纹分叉破坏,呈现出镜面雾化羽毛平纹特征;含深度30mm单内裂纹试样发生Ⅰ-Ⅱ-Ⅲ型复合扩展,断口为光滑的翼状扩展。(4)得到了破坏断口特征区尺寸与内裂纹深度关系的拟合公式。(5)KⅠ、KⅡ、KⅢ与内裂纹深度成反比关系;裂纹越远离试样中心,KⅠ越小,KⅡ、KⅢ越大;左右侧裂纹对中间裂纹的K值不影响。该研究表明3D-ILC可做为研究断裂力学中的内裂纹及复合裂纹问题的重要工具。

Al-3.5Cu-7Si合金拉伸断裂行为研究

观察了Al 3 5Cu 7Si合金拉伸断裂试样横截面的断裂路径 ,并结合力学性能试验对该合金的断裂行为进行了研究 ,总结了该合金中各种相的数量及形态对力学性能的影响。结果表明 ,除了高铸造气孔率明显降低该合金力学性能外 ,针状的硅相及由杂质铁产生的针状铁相 (FeSiAl5)是导致Al 3 5Cu 7Si合金力学性能下降的主要因素。固溶处理温度偏高造成的局部熔化微区会严重损害其力学性能 ,而少量未溶解块状θ相 (CuAl2 )对其力学性能无显著影响。

连接工艺对铝合金结构件力学性能的影响

对7B04铝合金回填式搅拌摩擦点焊及铆接连接的结构件的静力与疲劳性能进行对比测试.结果表明,由铆接与回填式搅拌摩擦点焊连接的典型结构的压缩静力载荷在117~124 kN范围内波动,剪切静载荷波动范围为89~95 kN,焊点间距对载荷的影响较小;铆接连接的典型件剪切疲劳寿命低于回填式搅拌摩擦点焊结构件寿命.对于点焊结构而言,接头微观组织不均匀导致硬度不均匀,同时搭接面处钩状结构向上弯曲,最终使得疲劳试件的失效主要沿轴肩回抽路径.

Notes on Multi-linear Variable Separation Approach

The multi-linear variable separation approach method is very useful to solve (2+1)-dimensional integrable systems. In this letter, we extend this method to solve (1+1)-dimensional Boiti system, (2+1)-dimensional Burgers system, (2+1)-dimensional breaking soliton system, and (2+1)-dimensional Maccari system. Some new exact solutions are obtained and the universal formula obtained from many (2+1)-dimensional systems is extended or modified.

Engineering Geological Assessment for Route Selection of Railway Line in Geologically Active Area:A Case Study in China

The Cheng-Lan railway links Chengdu, a central city in Southwestern China, and Lanzhou, a central city in Northwestern China. The railway passes through the Longmenshan fault zone (Wenchuan earthquake happened there on May 12, 2008), Minjiang fault zone, and Dongkunlun fault zone, which are all active. It runs over the Yangtze River and the Yellow River, and crosses high mountains and deep valleys. There exists, along the railway's alignment, different kinds of strata of hard granite and soft, weak metamorphic rocks such as carbonaceous slate, schist, and phyllite. It is, therefore, a key issue for such an infrastructure construction to assess the engineering geological conditions and risks, so as to mitigate or avoid possible georisks and to offer optional designs. Geological survey and georisk assessment along the railway corridor are carried out. Special attention is given to active faults, earthquakes and seismic zones. Based on these, discussions about geological aspects for route selection of the railway are conducted and countermeasures for georisk control are proposed accordingly. Main conclusions are achieved as follows: (1) Geohazards such as landslides, rockfalls and debries flows dominate both the route selection of the railway and the engineering structures (e.g., tunnels or bridges) adopted; (2) Tunnel has been proved to be an excellent structure for linear engineering in geologically active area; and (3) In the case where avoiding is impractical, necessary protection measures should be taken to engineering slopes in high earthquake intensity areas, especially the area with earthquake of Ms. 8 or greater.

300M钢耳片拉伸强度与破坏机制

耳片是连接飞行器不同部位的关键零件,提升耳片的强度和准确计算不同耳片的承载能力对飞机减重和保证飞行安全具有重要意义。300M钢耳片由于强度高、韧性好在飞机起落架中得到了越来越广泛的应用。然而,我国《飞机设计手册》中并没有给出准确计算300M钢耳片拉伸强度的效率系数,也不清楚各种耳片失效模式的原因。为此,设计了不同形式和几何尺寸的耳片,开展了不同加载角度拉伸破坏试验,获得了耳片拉伸极限载荷和破坏模式。在此基础上,给出了300M钢耳片拉伸强度效率系数的计算公式,建立并验证了300M钢耳片拉伸极限载荷分析的弹塑性有限元方法,仿真预测的极限载荷误差小于8%。结合试验结果揭示了300M钢耳片的破坏机制,基于J_(2)弹塑性本构模型和临界等效塑性应变断裂准则,开发VUMAT子程序模拟了3种典型断裂路径。