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3Cr2W8V钢热疲劳裂纹长大方式的原位观察

刘剑虹 , 何世禹 , 姚枚

金属学报

在TS-2型台式扫描电子显微镜中,装入自制的微型热疲劳试验装置,观察了3Cr2W8V钢热疲劳裂纹长大过程,结果表明:热疲劳裂纹长大前,主裂纹尖端首先钝化,在其前方出现孔洞或不连续微裂纹,热疲劳裂纹的长大通过主裂纹与孔洞及微裂之间的桥接方式进行。

关键词: 3Cr2W8V钢 , thermal fatigue , crack growth , in situ observation

45钢疲劳短裂纹的形成和扩展

徐灏 , 吴志学

金属学报

本文对４５钢光滑试样疲劳短裂纹的形成和扩展进行了试验，利用复型技术和光学显微镜观测了裂纹尺寸演化全过程．发现疲劳短裂纹形成寿命小于失效寿命的１０％．根据裂纹的扩展速度将短裂纹形成分成微观短裂纹和物理短裂纹两个阶段，给出了区分两种短裂纹的裂纹特征尺寸值和两种短裂纹的扩展速度公式

关键词: ４５钢 , fatigue. short crack , crack growth , null

Ü690合金在高温水中的应力腐蚀裂纹扩展行为

但体纯吕战鹏王俭秋韩恩厚庄子哲雄柯伟

金属学报 doi:10.3724/SP.J.1037.2010.00199

用交流电位降(ACPD)技术实现了模拟压水堆一回路340℃高温水环境中690合金应力腐蚀裂纹扩展的实时监测. 断口观察表明, 2种一维冷加工690合金均出现沿晶应力腐蚀裂纹扩展, 裂纹沿平行轧制方向的扩展速率略高于垂直轧制方向的速率; 当溶解H浓度(C_dH)由30 μL/g减小到10 μL/g时, 经1075℃退火和700℃固溶处理15 h并一维冷轧25%的T-L取向690合金的平均裂纹扩展速率由4.8×10^-11 m/s增加至11.2×10^-11 m/s; 应力腐蚀裂纹扩展主要为内氧化机制.

关键词: 应力腐蚀 , crack growth , alternative current potential drop(ACPD)  , high–temperature water

莫来石陶瓷的室温应力腐蚀开裂行为

杜春生 , 龚江宏 , 杨正方 , 袁启明

无机材料学报

分别在空气、蒸馏水和碱性溶液中测定了莫来石陶瓷材料在不同外加应力水平下的室温断裂寿命，探讨了应力腐蚀裂纹缓慢扩展机理．研究表明，在高载荷下，吸附效应为裂纹扩展的主导机理，而在低载荷下，裂纹尖端钝化效应为主导机理．此外，在蒸馏水和碱性溶液两种介质中裂纹扩展指数N值有所不同，反映了介质对水合层的不同溶解能力．

关键词: 应力腐蚀 , crack growth , mullite ceramics

天然橡胶/顺丁橡胶共混胶体系裂纹生长行为的形态演变机理

刘衍朋 , 翁更生 , 姚鸿 , 常爱军 , 付坤 , 陈忠仁 , 刘欣 , 张慧慧

高分子材料科学与工程

研究了不同共混比例的顺丁橡胶(BR)与天然橡胶(NR)组成的共混胶的裂纹尖端生长行为.采用裂纹扩展在线研究平台(DMA-Crack Growth)、超高速摄像仪、扫描电子显微镜和扫描探针显微镜对裂纹尖端进行实时追踪观测,拍摄不同共混比例的橡胶裂纹尖端的裂纹扩展动态图像.结果表明,共混比例达到m(BR)/m(NR)=50/50时,韧带均匀分布在裂纹尖端,韧带多而细且均匀,可以有效减缓橡胶裂纹扩展速度;橡胶开裂的断面随着BR共混比例的增加,表面形貌由类三角形向扇形形貌过渡.最后讨论了裂纹增长的机理.

关键词: 橡胶 , 共混 , 裂纹扩展 , 演变机理

CRACK GROWTH BEHAVIOR AND FRACTURE FEATURE OF GH2132 UNDER CREEP-FATIGUE CONDITIONS

M.F. Geng(Luoyang Ship Material Research Institute , Luoyang 471039 , China)

金属学报(英文版)

The crack growth behavior and fracture feature of superalloy GH2132 (equivalent to A286) under creep-fatigue conditions have been studied in the present paper. The tests were carried out at 550℃ under various cyclic freqencies (hold time) and load levels,and the fracture surfaces were examined by using a scanning electron microscope. It is shown that the fracture mode of creep-fatigue and the effect of cyclic loading on crack growth change with the growth of crack and the increase of net-section stress,and both are reversed when the net-section stress is up to the yield stress of material.When σn <σ0.2, cracking is predominantly cycle-dependent transgranular and cyclic loading accelerates creep crack growth, whereas when σm>σ0.2, the case is reversed.

关键词: creep-fatigue , null , null , null , null , null

CRACK GROWTH, FRACTURE FEATURE AND RUPTURE LIFEDURING CYCLIC CREEP OF SUPERALLOY GH2132

Author M.F. Geng1) , T. Wang1) and X.A. Zhang2) 1) Department of Special Metal Materials and Products , Luoyang Ship Material Research Institute , Luoyang 471039 , China2) Mechanical Properties Laboratory , Beijing Institute of Aeronautical Materials , Beijing 100095 , China Manuscript received18 October 1998

金属学报(英文版)

The effects of cyclic loading on crack growth, fracture feature and rupture life of superalloy GH2132 have been studied in the present paper. The crack growth tests were carried out at 550 on compact tension specimens under a wide range of load levels and various periods of hold time, and the fracture surfaces were examined on a scanning electron microscope. The results show that, for both static and cyclic creep, Stage-I of crack growth is related with initial test stress, during which the crack extension is about 0.5mm, and that the final effect of cyclic loading on rupture life depends on the counteraction of its two reversed effects on crack growth rate before and after the point n=0.2.

关键词: cyclic creep , null , null , null , null , null

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