共查询到19条相似文献,搜索用时 46 毫秒
1.
4.
显微组织对珠光体钢疲劳裂纹扩展速率的影响 总被引:3,自引:0,他引:3
用金相显微镜、扫描电镜(SEM)及带有切口的三点弯曲试样研究了显微组织对珠光体钢疲劳裂纹扩展速率的影响。结果表明:共析珠光体钢中的疲劳裂纹扩展速率da/dN取决于珠光体层片间距。细化珠光体层片间距可有效减缓共析珠光体钢中的疲劳裂纹扩展速率,尤其在高应力场强度因子幅值△K作用的情况下;珠光体钢的疲劳裂纹扩展速率与断裂前的△K之间的关系为:da/dN=6.94×10~(-9)(△K)~(2.919) (mm·c~(-1));显微组织中存在一定量的先共析铁素体可显著降低珠光体钢中疲劳裂纹的扩展速率。 相似文献
5.
在光学显微镜下对TC4-DT钛合金电子束焊接头显微组织进行了分析,讨论了接头不同位置显微组织特征.比较了疲劳裂纹始于焊接接头不同位置时的宏观裂纹扩展路径及裂纹扩展速率,依据焊接接头显微组织特点讨论了显微组织对疲劳裂纹扩展行为的影响.结果表明,电子束焊接头沿熔深方向显微组织存在一定的差异;文中条件下,与母材区相比焊缝熔合区及热影响区具有较高的疲劳裂纹扩展抗力,导致裂纹扩展路径逐步偏向母材区,最后讨论了裂纹扩展路径的偏折对裂纹扩展速率的影响. 相似文献
6.
TA15钛合金疲劳裂纹扩展与显微组织的关系 总被引:2,自引:0,他引:2
对TA15钛合金的疲劳裂纹扩展速率及其影响因素进行了研究.结果表明,在β区锻造的模锻件,其低倍组织为清晰可见的β晶粒,属于较粗大的网篮组织.在α β区锻造的模锻件,其组织为双态组织.β区锻件的塑性偏低,但其da/dN疲劳裂纹扩展速率明显比α β区锻件的慢.β区锻件的da/dN疲劳裂纹的断口形貌中,包括裂纹扩展的初期、中间阶段和末尾断裂阶段,都明显存在二次裂纹和解理脆性特征. 相似文献
7.
8.
在裂纹第一阶段区域的附近进行了裂纹扩展试验,试验在三种不同基体组织的球墨铸铁上进行,基体组织分别为铁素体、牛眼状铁素体和珠光体,抗拉强度分别为380,500和700MPa。铁素体基体球墨铸铁的裂纹扩展速度da/dN随着应力场强度因子△K的下降而连续下降;另一方面,牛眼状铁素体和珠光体基体的球墨铸铁在裂纹扩展速度da/dN-△K图上呈现出不连续下降。将试验结果与根据断裂力学计算出局部裂纹尖端的△K计算结果进行了比较。在从da/dN-△K图上在不连续下降的下段△K的计算结果与假定裂纹尖端拉一压区域有一颗石墨球用断裂力学计算出的结果相当吻合。但是,如果假定在周期性的应力集中区域含有多个始末颗粒,铁素体基体球墨铸铁的计算值小于△Km。可以相信球墨铸铁的疲劳断裂机理受到石墨颗粒间距,裂纹尖端塑性区域和石墨颗粒周围的应力集中的显著影响。 相似文献
9.
10.
11.
FATIGUE CRACK PROPAGATION IN Al-Li ALLOY 8090 总被引:1,自引:0,他引:1
WANG Zhongguang ZHANG Yun HU Zhuangqi State Key Laboratory for Fatigue Fracture of Materials 《金属学报(英文版)》1992,5(6):436-442
Fatigue crack growth rates of Al-Li alloy 8090 in air were found to be strongly dependent up-on the aging conditions.The naturally aged and underaged specimens showed the highest re-sistance to the fatigue crack propagation.The fatigue crack growth resistance of the overagedspecimen is the lowest and that of the peakaged specimen in between.As compared to air,3.5% NaCl solution does not change the effect of aging conditions on the fatigue crackgrowth,but causes a decrease of the resistance to the fatigue crack growth under the same ag-ing condition.Both short cracks from notch and physically short cracks showed much higherrates of fatigue crack propagation in comparison with long cracks under the same aging condi-tion and stress intensity level.The growth behavior of the short crack depends on its type.Thegrowth rate of short crack from notch decreases first to a minimum and then increases with in-creasing △K.However,the physically short crack grows at a progressively increasing rate.The effects of aging conditions are explained in terms of the slip planarity of dislocations andthe cyclic slip reversibility.The observed short crack behavior is considered to be dependent onthe crack closure and the local plasticity near the crack tip. 相似文献
12.
研究了8090型Al—Li合?疲劳裂纹扩展行为以及组织结构和环境的影响,结果表明,在空气中,自然时效和欠时效?现出最好的疲劳裂纹扩展阻力,其次是峰时效状态,而过时效状态的疲劳裂纹扩展阻力最低,在3.5%NaCl水溶液中,时效状态对疲劳裂纹扩展行为有着同空气中相同的影响规律,但在同样的时效条件下,在3.5%NaCl水溶液中的疲劳裂纹扩展阻力要比空气中的低,在相同的应力强度因子范围△K作用下,缺口短裂纹和物理短裂纹均表现出比长裂纹高的扩展速率,用位错的平面滑移性和循环滑移可逆性解释了时效的影响,用裂纹的闭合效应和裂纹尖端塑性区尺寸说明了长短裂纹扩展行为的差别。 相似文献
13.
14.
BEHAVIOUROFINITIATIONANDGROWTHOFSHORTFATIGUECRACKSWUZhixue;XUHao(InstituteofMechanicalEngineering,NortheasternUniversity,Shen... 相似文献
15.
DENG Rongying ZHOU Aihua JIANG Huaiqing LI Chunxiu Institute of Mechanics Academia Sinica Beijing ChinaZHANG Liqing SUN Yutian Beijing Institute of Engineering Beijing China Originally published in ACTA METALL SIN 《金属学报(英文版)》1989,2(6):439-443
The effect of pearlite interlamellar spacing(d)from 0.31 to 0.77 μm of T8 steel on fatiguecrack propagation near threshold has been investigated at different stress ratios(R).Theclosure stress intensity factor(K_(cl)),the threshold value(ΔK_(th))and crack tip opening dis-placement range(ΔCOD)were measured.The results show that pearlite interlamellar spac-ing in this range has no effect on K_(cl),but has effect on the threshold value in low stress ratio.The threshold value is higher for materials with larger interlamellar spacing.No matter whatthe stress ratio is,during the propagation near threshold,the propagation rate will be thesame,provieded the crack tip opening displacement range is the same.Metallurgical examinations were also carried out to show that the crack propagationpath is sensitive to mierostructure.The crack always propagates along either boundary ofpearlite colony or ferrite lamellar in pearlite. 相似文献
16.
本文研究铁素体-马氏体复相钢中铁素体含量对裂纹萌生、扩展和裂纹尖端塑性变形的影响。在24.2—41.5%的铁素体含量范围内,以33.8%含量的复相钢裂纹萌生期N_0较长、门槛值ΔK_(th)高、并有低的扩展速率和较高的闭合应力强度因子K_(Cl)。三种铁素体含量复相钢的dα/dN-ΔK_(eff)一致的事实,表明裂纹闭合对低速扩展的重要作用,且闭合程度(K_(Cl)/K_(max))随裂纹尖端ΔK的降低而提高,在ΔK_(th)时达到最大。铁素体含量为33.8%的K_(Cl)/K_(max)值最高达0.7。 相似文献
17.
以紧固孔结构件腐蚀疲劳试验为基础,研究了腐蚀疲劳裂纹虚拟扩展方法即随机过程和AFGROW模拟方法.以试验数据拟合得到的Paris公式为基础,在随机过程方法中考虑了正态随机过程和对数正态随机过程,得到裂纹长度和循环数之间的模拟曲线,给出指定循环数下裂纹长度的概率模型并和实验结果进行了比较.利用AFGROW对腐蚀疲劳裂纹扩展进行了模拟,裂纹扩展模拟曲线与实验值符合较好. 相似文献
18.
19.
PEI Hongxun Institute of Corrosion Protection of Metals Academia Sinica Shenyang China Institute of Corrosion Protection of Metals Academia Sinica Shenyang China 《金属学报(英文版)》1989,2(4):284-292
Based on the experimental study of complex biaxial mode Ⅰ fatigue crack growth and thediscussion on Von Mises'theory,a new approach is proposed for correlating crack propaga-tion rate under both in-phase and out-of-phase biaxial stress cycling.The results emphasizethe contribution of plasticity to fatigue crack growth. 相似文献