退火工艺对钨丝/锆基非晶合金复合材料动态力学性能及断裂模式的影响

研究了体积含量为60％的钨丝/锆基复合材料在经过退火处理后,材料的应力-应变响应和动态断裂特征以及断口形貌。利用Hopkingson压杆冲击加载装置和扫描电镜(SEM)以及X射线衍射仪(XRD),对Φ5mm×5mm的圆柱形试样进行了相关研究。研究表明,钨丝体积含量为60％的钨丝/锆基复合材料在经过退火处理后,非晶基体出现了明显的晶化现象;材料在退火后动态压缩强度比退火前有明显降低;退火后非晶基体断口形貌由退火前的完全的脉络花样转变为河流花样和脉络花样混合模式;经过动态冲击后,钨丝的断裂模式在退火前后变化大。     

某船用钢动态断裂行为的温度效应

在高加载速率条件下,利用Hopkinson杆型动态断裂韧度测试装置测定了某船用钢在不同温度下的动态断裂韧度,首次获得了该钢动态断裂韧度随温度的变化规律,即随着温度降低,动态断裂韧度呈现明显的上下平台及韧脆转变特征.断口形貌则由上平台的微孔型延性断口、韧脆转变区的混合断口过渡到下平台的解理断口.同时,测定的动态断裂韧度值也为该钢在高加载速率条件下的韧脆转变行为及安全性评定提供了定量依据.     

改善块体金属玻璃室温脆性的研究进展

块体金属玻璃有许多优良的性能,如高强度、高硬度、高比强度、好的耐腐蚀抗力以及优良的软磁性能等。然而,近乎于零的室温塑性应变严重限制了其作为结构材料的实际应用。总结了近年来改善块体金属玻璃室温脆性的最新研究进展,并对这些方法的优缺点进行了分析。     

飞机腹鳍根部型材疲劳断裂强度分析

针对某型飞机腹鳍根部型材疲劳断裂问题,依据腹鳍的结构和工作特点,应用疲劳断裂理论进行定量分析,排除了因飞行中所受空气动力引起的静载和动载造成损伤的可能性,分析了其裂纹产生原因并提出使用维修建议.     

激光产生的激波在靶材中的传播及层裂效应

应用一维理想弹塑性流体力学模型 ,通过有限差分方法 ,研究了XeCl准分子脉冲强激光辐照固体靶材时 ,表面烧蚀压力在靶材中产生的激波的形成、持续和衰减过程 ;并应用累积损伤判据和动态断裂准则 ,分别计算了金属铝和碳酚醛靶材的层裂损伤。对有关实验数据给出合理的理论解释     

Studies on the nutritive characteristics and fracture resistance to compressive loading of selected bambara groundnut lines

Extensive laboratory experiments were conducted to determine the nutritive characteristics and fracture resistance to compressive loading of some bambara groundnut lines. Data obtained showed percentage carbohydrate, protein and oil contents of 52.60, 17.52 and 6.66 respectively for dehulled bambara groundnut seeds as against lower percentage values of 48.60, 16.99 and 6.20 obtained from the analysis of whole seeds of BgB-Br. Investigations on the mechanical properties revealed that the force needed to rupture the seeds was influenced by moisture content and loading position of the seeds. The force was found to decrease from 262 to 100 N with increase in moisture content, while the deformation increased from 1.9 to 4.5 mm with increase in moisture content. Maximum toughness occurred at different moistures which represent the moisture levels for absorbing compressive energy which are important for resisting mechanical damage during handling of the bambara groundnut lines. © 1999 Society of Chemical Industry     

人工股骨头置换术治疗高龄股骨转子下骨折

转子下骨折的高龄患者,常合并多种基础性疾病,如采用内固定治疗,患者一般需卧床5至8周才能扶拐部分负重行走,仍易产生坠积性肺炎、褥疮、泌尿系感染、深静脉血栓等严重并发症。本文探讨运用人工半髋关节置换术治疗高龄患者股骨转子下骨折,旨在实现让患者早期下床功能锻炼,减少长期卧床并发症的目的。     

超高强度钢疲劳塑性区内的应变诱发马氏体相变

对一种低碳马氏体型超高强度钢疲劳断口薄膜试样的电子衍射分析表明,疲劳塑性区内的残余奥氏体在交变应力的作用下转变为马氏体.本文就这种应变诱发相变对疲劳性能的作用机理进行了分析讨论.     

Adhesion strength of leadframe/EMC interfaces

Cu-based leadframe sheets were oxidized in alkaline solutions to produce brown and/or black oxide on the surfaces, and molded with epoxy molding compound (EMC). The adhesion strength of leadframe/EMC interface was measured using sandwiched double-cantilever beam (SDCB) specimens and pull-out specimens. Results showed that the adhesion strength of leadframe/EMC interface was inherently very poor but could be increased drastically with the nucleation of acicular CuO precipitates. The presence of smooth-faceted Cu₂O on the surface of the leadframe gave close to zero fracture toughness (G_C) and suitable pull strength (PS). A direct correlation between G_C and PS showed that PS can be a measure of G_C only in a limited range.     

纯锡的速率相关性变形行为

考察了纯锡在拉伸载荷下的力学性能及形变,探讨了应变速率对纯锡的变形机制的影响。采用扫描电镜形貌观察,对比不同应变速率(0.001~0.1 s–1)下样品表面的晶粒形貌、形变特征、断口信息。发现在较低的应变速率(0.001 s–1)下,纯锡的形变机制以蠕变为主要模式;在较高的应变速率(0.1 s–1)下,形变机制以位错滑移为主要特征。