材料科学技术（英）
Using a fractal model, we give a new interpretation of the reversed sigmoidal curves of fracture surface profile length obtained in some experiments. It is pointed out that a single parameter (fractal dimension D) is not sufficient to characterize a fractal curve completely. It is shown that the initiator length L-0 is also important to characterize a fractal curve. We have derived a formula which correlate the fracture energy with the fractal parameters of the fracture surfaces and analyzed some experimental data.
关键词:
fractography
Journal of Physics D-Applied Physics
Fractal dimensions of different parts of a fracture surface formed by slow stable crack propagation, induced by the combined effect of hydrogen and static bending moment, were determined using the method of fracture profile analysis. The results showed that the fractal dimension increases with increasing transgranular fracture which increases as the crack propagates. This means that the increase of the fractal dimension responds to the increase of the energy needed to form the fracture surface, and in our case the process of forming a fracture surface by slow stable crack propagation is one of increasing fractal dimension of the fracture surface; when the fractal dimension reaches a critical value, the crack propagation becomes unstable.
关键词:
fractography
S.Q. Li
,
J.I. Dickson and J.P. Bailon (Central Iron and Steel Research Institute (CISRI)
,
Beijing 100081
,
China)(Ecole Polytecnique de Montreal
,
Montreal H3C 3A7
,
Canada)
金属学报(英文版)
The microfractography of transgranular stress corrosion cracking (TSCC) of 70Cu-30Zn a-brass in ammoniacal solution was studied. The observations indicate that on a very microscale, the crack path of TSCC of or-brass follows {111} planes. The crack path very often alternates between {111} Planes to result in "cleavage-like"facet, the usual average orientation of which is {110} with preferential microscopic crack propagation in (100) and (112) directions. The average orientation of wide secondary facets is often close to {100}. The size of {111} microfacets increases with incrmsing stress intensity K, which indicates that the microscopic crack path follows {111} planes on which some localized slip has occurred. Possible TSCC mechanisms which appear to be consistent with the microfraphic features observed in the present study are also discussed.
关键词:
fractography
,
null
,
null
,
null
WU Huaisheng ZHONG Qunpeng Jiangsu Institute of Technology
,
Zhenjiang
,
212013
,
ChinaBeijing University of Aeronautics and Astronautics
,
Beijing
,
100083
,
China
材料科学技术（英）
Under the constant amplitude and pro- grammed loading conditions the fatigued fracture surfaces of 2024-T3 sheet are examined by SEM and TEM.A corrected method,in which the effects of loading sequence are taken into account,has been developed for the retrieval of effective stress spectrum.The parameters including d,a,C,n,R,α and σ_y are evaluated according to their influences on the retrieved results.Several computer programs have been produced for the fractographic quantita- tive analysis,and the application of image pro- cessing technique in the fractographic analysis is al- so interpreted.
关键词:
fatigue
,
null
,
null
,
null
,
null
刘兵
,
何国球
,
蒋小松
,
向学渊
,
胡正飞
,
朱旻昊
材料科学与工艺
为了解微动疲劳失效机理,通过柱面对柱面的接触方式,研究了60Si2Mn钢在椭圆形路径、拉扭耦合作用下的多轴低周微动疲劳特性,深入分析讨论了不同轴向循环拉伸应力幅值对摩擦磨损表面和断口形貌的影响.结果认为：磨损区产生的氧化物磨屑对微动区磨擦损伤行为具有显著影响;微动摩擦磨损对试样表面的影响深度只有数十微米;微动疲劳裂纹源形成于微动摩擦磨损区的边缘;裂纹源有氧化现象发生,并附着有细小的氧化物磨屑.
关键词:
微动疲劳
,
磨擦磨损
,
失效分析
,
断口形貌
刘兵
,
何国求
,
蒋小松
,
向学渊
,
胡正飞
,
朱曼昊
材料研究学报
饬?0Si_2Mn钢在拉扭复合载荷作用下的低周微动疲劳特性,研究了不同轴向循环拉伸应力幅值对微动疲劳寿命、循环软化特性以及摩擦磨损表面和断口形貌的影响.结果表明,随着循环拉伸应力幅值的提高,60Si_2Mn钢的微动疲劳寿命降低幅度不同,发生循环软化的时期不断提前,完成循环软化的疲劳周期也不断缩短.同时,微动摩擦副产生的氧化物磨屑对微动磨损性能有重要影响,在疲劳前期加剧摩擦磨损,在疲劳后期减轻摩擦磨损.微动疲劳裂纹源形成于试样发生微动摩擦磨损的表面,并出现疲劳台阶.在扭矩产生的切向剪切应力作用下,疲劳裂纹沿着与轴向45°角的方向扩展,最终在断口上留下显著的舌状凸起,拉应力的幅值越大舌状凸起越明显.
关键词:
属材料
,
微动疲劳
,
疲劳寿命
,
循环软化
,
断口形貌分析
郭跃岭
,
韩恩厚
,
王俭秋
金属学报
doi:10.11900/0412.1961.2014.00466
利用电子背散射衍射(EBSD)和显微硬度(Hv)测量技术,表征了原始态、锻造固溶处理态和锻造去应力处理态316LN不锈钢(316LNSS)的显微组织和残余应变.利用U型弯曲应力腐蚀评价方法,研究了3种材料在325℃,3.5％NaOH溶液中的应力腐蚀开裂(SCC)行为的差异.结果表明,原始态316LNSS的SCC数量最多,裂纹扩展速率最大,而锻造固溶处理态316LNSS的SCC敏感性最低;原始态和锻造固溶处理态的316LNSS在高温碱性溶液中发生明显的沿晶应力腐蚀开裂(IGSCC),而锻造去应力态的316LNSS发生混合型SCC;去应力处理不能有效消除锻造过程中可能产生的条带组织,不利于316LNSS整体抗SCC性能的提高.
关键词:
不锈钢
,
核电材料
,
应力腐蚀开裂
,
高温碱性溶液
,
断口形貌
王辉
,
陈明和
,
张成祥
,
赵海艳
,
王鹏飞
,
雷晓晶
航空材料学报
doi:10.11868/j.issn.1005-5053.2016.5.013
采用不同应变速率(0.0001~0.1s-1)下单轴拉伸实验对 GH39合金应变硬化行为与断口特征进行了研究。结果表明：应变硬化指数在不同应变量下表现出多重性,真应力应变不完全遵循 Hollomon 对数线性关系。塑性变形开始阶段,应变硬化指数n为恒定；真应变ε在0.014~0.13,n随着应变的增加而增加,在此过程由于形成大量形变孪晶,孪晶与位错相互作用,硬化能力增强；随着应变速率的提高,材料的应变硬化指数略下降；在低应变速率时段合金的拉伸断口为延性断裂,随着应变速率的增加从韧窝状延性断裂向半解理断裂过渡。
关键词:
GH39合金
,
形变孪晶
,
应变硬化
,
应变速率
,
断口形貌
李国爱
,
张坤
,
陆政
,
何维维
稀有金属材料与工程
采用拉伸试验机、金相显微镜、XRD、SEM以及EMPA等手段对合金元素总含量超过15％(质量分数,下同)的新型超高强Al-11.7Zn-2.2Mg-2.0Cu-0.12Zr铝合金不同固溶温度处理后的组织与性能变化规律进行了研究.结果表明:晶内的固溶度随温度升高逐渐增加,在474℃时基本达到稳定状态,约有99％的Zn、Mg以及75％的Cu溶入晶内,其余的合金元素富集在晶界第二相内,此时,第二相主要由含Cu的η以及T相构成;合金的最佳固溶温度为474℃,此时合金的抗拉强度(σb)为688 MPa、延伸率(δ)为8％;温度为476℃时,合金局部区域出现轻微过烧,导致延伸率迅速降低;断口分析显示,随固溶温度的提高,再结晶程度增加,晶界第二相数量减少,合金的拉伸断口由较低温度时的沿晶+穿晶混合断口转变为较高温度时的沿晶断口为主.
关键词:
Al-Zn-Mg-Cu-Zr合金
,
固溶温度
,
第二相粒子
,
再结晶
,
断口形貌
