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Effects of microstructure on the fatigue crack growth behavior of light metals and design considerations
Gavras, Anastasios G.;Chenelle, Brendan F.;Lados, Diana A.;
Matéria (Rio de Janeiro) , 2010, DOI: 10.1590/S1517-70762010000200033
Abstract: fatigue crack growth mechanisms of long and small cracks were investigated in cast and wrought aluminum and titanium alloys with various microstructures (as-cast a535, 6061-t61, and mill-and beta annealed ti-6al-4v). in addition, friction stir welded and cold spray processed 6061-t61 were also investigated. the effects of microstructure on the fatigue crack growth response of each material were evaluated. long crack growth data were generated on compact tension specimens at low and high stress ratios r=0.1 and 0.7, respectively. small crack growth testing was performed on corner and surface flaw tension specimens at low stress ratio, r=0.1. fatigue crack growth mechanisms at the microstructural scale of the materials were identified and will be discussed. closure corrections were applied to long crack growth data, and the results were compared to experimental small crack growth data. models for small crack growth predictions from long crack growth data will also be presented and discussed.
Design fatigue curves based on small crack growth and crack closure  [PDF]
Somnath Chattopadhyay
Journal of Applied Science and Engineering Technology , 2008,
Abstract: The propagation behavior of short cracks cannot be studied by linear elastic methods because of the large plastic region near the crack tip, as well as a break down in correlation of the stress intensity factor with the fatigue crack growth rates. The proposedfatigue design approach incorporates a distanceparameter in conjunction with linear elastic fracture mechanics and effectively integrates long and short crack growth test data. This distance parameter is a material constant, which allows for the effects of (a) large-scale plasticity, (b) crack closure,and (c) fatigue crack threshold. Furthermore, this parameter successfully predicts fatigue crack growth behavior of short cracks. The practical applicationof this method is for studying fatigue crack initiation in pressure vessels and is based on the concept that initiation occurs only when the material ahead of the crack tip is damaged enough by cyclic straining. In this paper, the initiation and growth of small cracks have been investigated along with consideration for crack closure. These results provide the design fatigue curves for some typical structural materials and lead to realistic estimates of fatigue lives for materials used in pressure vessels.The techniques outlined in this paper are equally applicable to materials used in aerospace and automotive industries.
FATIGUE CRACK PROPAGATION IN Al-Li ALLOY 8090
WANG Zhongguang ZHANG Yun HU Zhuangqi State Key Laboratory for Fatigue,Fracture of Materials,Institute of Metal Research,Academia Sinica,Shenyang,ChinaHE Shiyu LI Qingjian Harbin Institute of Technology,Harbin,China,

金属学报(英文版) , 1992,
Abstract: 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.
ДЕФОРМАЦ ЙНИЙ РЕЛЬ Ф У ЗОН ВТОМНО ТР ЩИНИ Deformation relief in the area of fatigue crack Деформационный рельеф в зоне усталостной трещины
М.В. Карускевич,О.Ю. Корчук,Д.О. Кириленко
Proceedings of National Aviation University , 2007,
Abstract: Подано результати спостереження стану поверхн плакованого алюм н вого сплаву поблизу втомно тр щини. Показано, що деформац йний рель ф поблизу концентратор в напружень показником утомного пошкодження матер алу не лише на нкубац йн й стад втоми, але й на стад поширення маг стрально тр щини. К льк сним показником, який характеризу законом рност розвитку тр щини втоми, параметр пошкодження D, який визнача насичен сть поверхн ознаками м кропластично деформац . Results of observation of the alclad aluminium alloy surface state near fatigue crack are presented. It is shown, that deformation relief near stress concentrator expresses fatigue damage of the material not only at the initial stage of fatigue, but at the fatigue crack propagation stage as well. The damage parameter D, that determines the intensity of the surface micro plastic deformation features can be considered as quantitative parameter of fatigue crack propagation rate. Представлены результаты наблюдения состояния поверхности плакированного алюминиевого сплава вблизи усталостной трещины. Показано, что деформационный рельеф вблизи концентраторов напряжений является показателем усталостных повреждения материала не только на инкубационной стадии усталости, но и на стадии распространения магистральной трещины. Количественным показателем, который характеризует закономерности развития трещины усталости, есть параметр повреждения D, который определяет насыщенность поверхности признаками микропластической деформации.
FATIGUE CRACK PROPAGATION IN Al-Li ALLOY 8090
8090Al—Li合金的疲劳裂纹扩展

WANG Zhongguang,ZHANG Yun,HU Zhuangqi,HE Shiyu,LI Qingjian State Key Laboratory for Fatigue,Fracture of Materials,Institute of Metal Research,Academia Sinica,Shenyang Harbin Institute of Technology,Correspendent profersor,Insitute of Research,Acodemia Sinica,Sheyang,
王中光
,张匀,胡壮麒,何世禹,李清健

金属学报 , 1992,
Abstract: Fatigue crack growth rates of 8090 type Al-Li alloy in air were found to be strongly dependent upon the aging conditions. The naturally aged and underaged specimens showed the highest resistance to the fatigue crack propagation. The fatigue crack growth re- sistance of the overaged specimen is the lowest and that of the peakaged specimen in between. As compared to air, 3.5%NaCl solution did not change the effect of aging conditions on the fatigue crack growth, but caused a decrease of the resistance to the fatigue crack growth un- der the same aging condition. Both short cracks from notch and physically short cracks showed much higher rates of fatigue crack propagation in comparison with long cracks under the same aging condition and stress intensity level. The growth behavior of the short crack depends on its type. The growth rate of short crack from notch decreases first to a minimum and then increases with increasing AK. However, the physically short crack grows at a progressively increasing rate. The effects of aging conditions were explained in terms of the slip planarity of dislocations and the cyclic slip reversibility. The observed short crack behav- ior was considered to be dependent on the crack closure and the local plasticity near the crack
A Statistical Model of Quantitative Relationship between Striation Spacings and Fatigue Crack Growth Rates
YANG Jingjun,KE Wei Institute of Corrosion,Protection of Metals,Academia Sinica,Shenyang,China To whom correspondence should be addressed,
杨京俊
,柯伟

材料科学技术学报 , 1989,
Abstract: Fatigue crack growth experiments were per- formed on A1 alloy LD 10 and Ti-6A1-4V alloy. Fatigue striation spacings and the deviation angles between the direction of micro-crack growth and that of macro-crack growth were quanti- tatively measured on fracture surface using scanning electron microscope. A statistical model of the relationship between striation spacings and fatigue crack propagation rates was developed on the basis of a statistical analysis of the deviation angles, Good agreement between experimental results and theoretical results calculated with the present model was obtained.
FATIGUE CRACK DEFLECTION AND FORMATION OF MICROCRACKS IN POROSITY AREA OF ZG42CrMo
ZG42CrMo缩松区疲劳裂纹的偏析和微裂纹的形成

赵芳欣,张瑛洁,张松,赵祖欣,尹绍奎,李德成
金属学报 , 1996,
Abstract: The fatigue crack propagation rates of ZG42CrMo and its porosity area were measured.The process of fatigue crack growth in porosity area was observed by using metallographic tracing method.Dislocation and slip at the tip of fatigue crack have been studied by using TEM.The morphologies of porosities and microcracks together with sulphide on the surface of porosities were researched by using EPM.Two effects of porosities which make crack deflection and catch crack on fatigue crack growth have been discussed.Possible mechanism of microcrack initiation has been analysed.
INVESTIGATION OF THE LOW-CYCLE FATIGUE AND FATIGUE CRACK GROWTH BEHAVIORS OF P91 BASE METAL AND WELD JOINTS
HCYang,YTu,MMYu,JZhao,
H.C.Yang
,Y.Tu,M.M.Yu,J.Zhao

金属学报(英文版) , 2004,
Abstract: Low cycle fatigue tests and crack growth propagations tests on P91 pipe base metal and its weld joints were conducted at three different temperatures: room temperature,550℃ and 575℃. The strain-life was analyzed, and the changes in fatigue life behavior and fatigue growth rates with increasing temperature were discussed. The different properties of the base metal and its weld joint have been analyzed.
Determination of K_1Stress Intensity Factors and Fatigue Crack Growth for Surface Crack in Auto-strengthened Thick-walled Ring Specimens
试验确定自增强圆筒的表面裂纹K1因子和疲劳扩展规律

Zha Zichu Wang Zhiqun Wang Junxu,
查子初
,王志群

实验力学 , 1991,
Abstract: An auto strengthened thick-walled ring specimen is developed.The stress in- tensity factors for surface crack in this specimen arc determined by compliance method.The relation between SIF at surface crack tip and compliance is given,and may be used as a reference to determine SIF for surface crack in other specimens.Aside from this,the fatigue crack growth rates and the shape variation of a growing surface fatigue crack in these speci- mens are also measured.
MICROFRACTOGRAPHY OF NEAR-THRESHOLD FATIGUE CRACK GROWTH
YANG Jingjun KE Wei Institute of Corrosion,Protection of Metals,Academia Sinica,Shenyang,China YANG Jingjun Institute of Corrosion,Protection of Metals,Academia Sinica,Wencui Road,Shenyang,China,
YANG Jingjun KE Wei Institute of Corrosion and Protection of Metals
,Academia Sinica,Shenyang,China YANG Jingjun Institute of Corrosion and Protection of Metals,Academia Sinica,Wencui Road,Shenyang,China

金属学报(英文版) , 1990,
Abstract: The fracture surface micromorphology in the near-threshold FCG region was studied in LD-10 aluminum alloy and Ti-6Al-4V allov.The SEM examinations reveal that the frac- ture surface of both alloys at low crack growth rates(1×10~(-7)-1×10~(-5)mm/cycle)takes on a cyclic facet appearance.The typical morphologies were either sawtoothedfacets or terraced facets for LD-10 aluminum alloy and isolated island facets for Ti-6Al-4V alloy.The mech- anism of near-threshold fatigue crack growth is explicated on the basis of experimental ob- servations.
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