• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Effect of Plastic Zone Size Induced by a Single Dwell Overload on the Fatigue Crack Growth Rate under Cyclic Loading

    2014-06-06 08:35:22WANGFangCUIWeichengHadalScienceandTechnologyResearchCenterShanghaiOceanUniversityShanghai201306China
    船舶力學(xué) 2014年9期

    WANG Fang,CUI Wei-cheng(Hadal Science and Technology Research Center,Shanghai Ocean University,Shanghai 201306,China)

    Effect of Plastic Zone Size Induced by a Single Dwell Overload on the Fatigue Crack Growth Rate under Cyclic Loading

    WANG Fang,CUI Wei-cheng
    (Hadal Science and Technology Research Center,Shanghai Ocean University,Shanghai 201306,China)

    Creep and fatigue are involved in the loading of deep manned submersible,which is a rather complex variable amplitude pattern.Reasonable assumptions should be made before calculating the room temperature dwell fatigue life.A typical simplified loading type is the cyclic loading with one period of overloaded dwell time.Retardation effects are observed in the prior experimental research while no proper prediction equations were proposed to explain the phenomenon.In this paper,a new prediction model for the load pattern of cyclic loading with a single dwell overload is proposed.Retardation is explained by the increase of monotonic compressive plastic zone size.The calculation methods of the total monotonic plastic zone size in the vicinity of crack tip,due to the overload and the dwell time are provided and the corresponding variation of crack opening level based on the total monotonic plastic zone can be obtained.Tests are conducted to obtain the parameters used in the crack growth models and creep models together with tensile test results of the material TC4 ELI, which is as an example to calculate the retardation effects of overload and dwell time.It is observed that the model can reasonably reflect the retardation effects due to compressive plastic zone in the vicinity of the crack tip induced by dwell time.

    crack growth rate;dwell overload;plastic zone size;manned pressure hull

    1 Introduction

    The pressure hull of deep manned submersibles during their service life will experience periods of both fluctuating and steady stresses.Hence,creep and fatigue are involved,which may act together in a synergistic manner.In order to obtain a proper fatigue design,it is important to consider the real structural loading history,P()t.Since fatigue failure is a future event,the fatigue loading history for the designed structure can never be known a priori.Many engineering methods are based on finding the worst case scenario,where‘worst’often should be interpreted as a certain severe load condition.Fig.1 gives a schematic representation of typical fatigue loading history with intermittent creep for pressure hull of deep manned submersibles.

    The fatigue failure with creep interaction has attracted attention especially in high temperature condition.Typically,linear accumulation model is used to consider the common interaction of fatigue and creep.In recent years,creep effect on fatigue in room temperature is also highlighted,which is often neglected in the past.

    In the past four decades,significant effort and progress have been made to study dwell fatigue and pure fatigue behavior of metal alloys to find out how the material responds to dwell time.The prior research attributed dwell sensitivity to many deleterious mechanisms.These mechanisms include:time-dependent strain accumulation,micro-structural and micro-texture influences,stress ratio effects,internal hydrogen embrittlement and environmental effects,crystallographic orientation dependence and interactions between creep and fatigue.However,there is no consensus on the basic cause of the dwell fatigue sensitivity of metal alloys,especially titanium alloys used in submersibles.Up to now,the problem remains opened as well on the scientific as on the engineer point of view.

    In 1980,Munz and Bachmann[1]proposed the separation idea to solve the problem.Fig.2 shows the separation of cycles with hold times in cycles with a triangular wave form and a constant load(dwell load).If such a separation is possible, the crack growth rate can be calculated by the addition of two terms:the crack growth rate(da/dN)tiangof a test with a triangular wave form an the crack growth rate da/dt in a constant load test at the stress intensity factor Kmax,corresponding to the maximum load,times the hold time Δt,

    Fig.2 Separation of load cycle with hold time[1]

    The linear summation in Eq.(1)is a simplified crack growth evaluation methods which hasbeen applicable to some structural integrity assessment procedure but has not considered the interaction between fatigue and creep damages.Wakai[2]conducted a benchmark study in predicting creep-fatigue crack growth in 316L(N)cracked plates subjected to a cyclic bending moment.The predictions according to different procedures using linear summation expression were compared with each other.Differences are found between the predictions of the methods. Comparing to the experimental data,it is found that the simplified methods exhibit conservatisms which are significantly reduced when integrating the creep curve continuously without initialization during the experiment.

    The load history shown in Fig.1 is a variable amplitude load pattern.However,due to the complexity to consider the variable amplitude problem,the load pattern must be simplified. Based on the results in literature,valuable results on the relationship of fatigue,creep and dwell fatigue at room temperature can be summarized as follows:

    (1)There will be a‘transition stress level’.The failure sequence among normal fatigue, creep and dwell fatigue will be different when the stress level is lower or higher than the transition stress level.At the lower stress level,the dwell fatigue life(cycles)will be approximate to the cyclic fatigue life(cycles),however,at the higher stress level around or higher than yield stress,damage accumulation will mostly exist in holding time period and the dwell fatigue life will be approximate to the room temperature creep life when the holding time in each cycle is relatively long.

    (2)There will be a‘saturated holding time’.At the higher stress level,the holding time length will affect the dwell fatigue life.When the holding time length(may be several minutes or hours)reaches to a certain value that we can call‘saturated holding time’,the dwell fatigue life(hours)will be largely approximate to the creep life(hours).when the holding time is a short period,the dwell fatigue life (cycles)will be approximate to the low-cycle fatigue life(cycles).

    According to the above conclusions, several assumption can be made before calculating the room temperature dwell fatigue life in the model for pressure hull submersibles as shown in Fig.1,in the following,

    (1)Most of the cycles at the lower stress level can be treated as normal cyclic loading as shown in the base triangle cycles of Fig.3(a);

    Fig.3 Schematic representation of the load patterns for (a)cyclic loading with one overload and(b)cyclic loading with overloaded dwell time

    (2)The cycle with holding time at the higher stress level can be treated as the single/multiple overload with a period of hold-ing time(cyclic loading with overloaded dwell time),as shown in Fig.3(b).

    So the cyclic loading with a single dwell overload is a typical simplified load pattern.Overload effect exists when holding stress is higher than base maximum stress.Room temperature creep at a crack tip and its influence on the fatigue crack growth behavior of a 304 stainless steel have been studied by Zhao et al[3].The load patterns of fatigue with dwell time shown in Fig.4 are considered in the test.A time-dependent deformation has been observed at the crack tips under various stress intensity factors.The deformation increases with increasing stress intensity factor.Either acceleration or retardation of fatigue crack growth rate is found after holding time, which depends on the load pattern.Retardation occurs in the load pattern A.A demarcation line is observed on the fracture surface following the holding period. This implies that the crack propagation root or mode changed after the dwell time.Improvement of the prediction equations should be proposed to explain more phenomenon of creep effect on fatigue crack growth rate.

    In this paper,a possible model is proposed to consider the load pattern shown in Fig.4(b), based on the unified fatigue life prediction method proposed by the authors’group[4].The study aims at searching for a proper method to consider the effect of plastic zone size induced by a single dwell overload on the fatigue crack propagation under cyclic loading.

    2 The model for cyclic loading with a single dwell overload

    Fig.4 A schematic of load patterns of fatigue with dwell time[3]

    The improved constitutive model can be expressed by Eqs.(2)[4].

    Considering this phenomenon that at higher load ratio the experimental data are closure free,we propose that the term ΔKeffin the constitution relation is expressed by the above piece-wise function.And Newman’s function[5]for fopis modified by introducing a constraint factor α′as follows:

    where A is a material-and environmentally-sensitive constant of dimensions(MPa)-2;m is a constant representing the slope of the corresponding fatigue crack growth rate curve;n is the index indicating the unstable fracture;KICis the plane strain fracture toughness of the material;KCfis the fracture toughness of the material under fatigue loading;reis an empirical material constant of the inherent flaw length of the order of 1 μm;a is the modified crack length which is equal to replus the actual crack length;σmaxis the maximum applied stress,σminis the minimum applied stress;Y(a)is a geometrical factor;Y(re)is a geometrical factor when a is equal to re;R is the stress ratio(=σmin/σmax);ΔKthis the threshold value of stress intensity factor range;ath is the threshold value corresponding to ΔKth;ΔKeffis the effective range of the stress intensity factor;ΔKeffthis the effective range of the stress intensity factor at the threshold level;Kopis the stress intensity factor at the opening level;α′is the crack tip stress/strain constraint ratio,which is 1 for the plane stress state and 1/(1-2v)for the plane strain state. The effect of n is significant only in the unstable propagation region;a constant value of 6 is recommended for a quick and simple engineering analysis.Eq.(4)can be used to determine the value of ΔKeffthand we recommend the values of β and β1are 0.4 and 0.36 respectively for titanium alloys.But the prediction error in the unstable region reflects the inaccuracy of the assumption of KCf=KIC.

    In considering overload effect,it is assuming that the single overload effect is due to variations in crack closure stress in metals and the large plastic zone as a result of overloading can raise the stress intensity factor at the opening level.A large plastic zone is created as a re-sult of an overload,and the crack closure level instantaneously rises to the maximum value, and then gradually recovers to the initial level under constant amplitude loading when the crack penetrates the large plastic zone in the subsequent cycles.A modified coefficient,Φ,on the basis of Wheeler model has been introduced as a magnification factor to correct the amount of the stress intensity factor at crack opening level during the recovering period after an overload in the improved constitutive model illustrated in Fig.5.

    Fig.5 Schematic representation of the assumed change of Kopunder load sequence with single overloading

    To account for the change of the crack closure level,a coefficient,Φ,is introduced in the improved constitutive model,

    Then it is important to estimate the plastic zone size in front of the crack tip first.Liu et al[6]proposed an equation to calculate the plastic zone size in front of the crack tip as follows:

    The plastic zone size mentioned above is also called monotonic plastic zone,which can be used to calculate the plastic zone due to one overload.As the minimum cyclic load in a cycle is approached,yielding in compression occurs in a region of a smaller size,called the cyclic plastic zone,as expressed in Eq.(7)[7]:

    Suppose that the single tensile overload and a short period of holding time will not induce crack propagation but just result in a monotonic plastic zone.Based on the assumption, Fig.6 is proposed to illustrate the plastic zone distribution due to the cyclic loading with overload dwell time.Among them,rdtis defined as the plastic zone increment due to dwell time. Then the total monotonic plastic zone can be expressed as the assumption of rOLand rdt.And Eq.(5)will be modified to,

    Fig.6 Schematic representation of the plastic zone due to cyclic loading with overloaded dwell time

    The physical mechanisms causing creep differ markedly for different classes of materials. In addition,even for a given material,different mechanisms act at various combinations of stress and temperature[8].During low temperature creep(<0.25Tm)of many metals and alloys,primary creep is the dominant deformation mode.At low creep stresses and creep strains(<2×10-3), the primary creep deformation of many metals and alloys has been described by a logarithmic creep law of the form ε=llnt+C.In cases where there is larger accumulation of primary creep strains,the deformation can be often described by a power law function of creep strain with time,

    where C and k are constants.And the dimension of T is second.

    According to the Ramberg-Osgood stress-strain curve,

    Creep deformation due to creep in room temperature is plastic

    deformation.And if thecreep strain is equivalent to the value due to monotonic stress σcreep,then the stress can be expressed as,

    Then the monotonic plastic zone can be simply modified to the following equation,

    where KOLCresults from the combined effects of an instant overload and the load holding time T,which can be expressed as follows:

    The above equation can be used to calculate the assumption of rOLand rdtduring the overload dwell time as follows:

    Then,the crack growth rate for the load pattern of Fig.4(b)can be calculated by combining E-qs.(2),(8)and(14).

    3 Example

    An example for a candidate titanium alloys used for deep manned submersibles,TC4 ELI will be used to show the application of the proposed model.The chemical compositions of the present tested sample of TC4 ELI,is given in Tab.1.Its tensile test results will not specifically illustrated here,which can be referred to Wang et al[9]Normal crack growth and creep tests are conducted first to obtain the room temperature creep parameters.All crack growth test specimens were conducted using a MTS810 servo-hydraulic testing machine.Standard C-T specimens with dimensions of B=12.5 mm;W=50 mm were cut and machined from three layers of 90 mm-thick hot rolled thick plate at three load ratios,i.e.0.0,0.5,0.8 to obtain date over a wide range of growth rates, with 2 specimens under each stress level,respectively from two sampling directions,parallel to rolling direction and vertical to rolling direction.Crack growth test results can be shown in Fig.7 together with the prediction curves using the unified crack growth rate model.

    Fig.7 Crack growth test results of TC4 ELI specimens

    Tab.1 Chemical composition of TC4 ELI(wt.%)

    Standard specimens were prepared for room temperature creep testing.The force is to be held constant for 84 hours.The creep strain or deformation is measured with time and the time rupture is recorded if this occurs during the test.The creep behavior for one specimen can be observed on a graph of displacement versus time as shown in Fig.8.There is an initial nearly instantaneous occurrence of elastic and perhaps also plastic deformation(or strain)followed by accumulation of creep deformation(or strain).Then the deformation rate d(Δl)/dt,hence the slope of the Δl versus t plot,is at first relatively high.However,the rate decreases and becomes approximately constant with time increasing.

    Fig.8 Normal creep test results of TC4 ELI

    Fig.9 Total results of creep strain versus time curves for normal creep of TC4 ELI

    Fig.9 gives the total results of creep strain versus time curves for normal creep of TC4 ELI. A relatively large scatter is observed comparing results for different specimens,which may result from different position and direction of the specimens as well as some discrepancy of microstructures of the specimens.The most conservative curve can be chosen for life analysis.Thenthe power law function of creep strain with time for TC4 ELI can be expressed as follows:

    Then all of parameters used in the crack growth models and creep models can be obtained together with tensile test results of the material,which are listed in Tab.2.Based on that,the crack length versus cycles curve under cyclic load pattern with one overload and a single dwell overload(10 minutes)can be obtained using the proposed model,as shown in Fig.10.It can be seen that retardation will occur under the effect of overload and a period of dwell time.It is from the compressive plastic zone in the vicinity of the crack tip.

    Tab.2 Parameters of crack growth rate model and creep model for Ti6Al4V ELI(R=0.1)

    Fig.10 Crack length versus cycles curve under cyclic load pattern with a single dwell overload(10 minutes)

    4 Summary and conclusions

    In this paper,a new prediction model for the load pattern of cyclic loading with a single dwell overload is proposed.The calculation methods of the total monotonic plastic zone size in the vicinity of crack tip,due to the overload and the dwell time are provided and the corre-sponding variation of crack opening level based on the total monotonic plastic zone can be obtained.Tests are conducted to obtain the parameters used in the crack growth models and creep models together with tensile test results of the material TC4 ELI,which is as an example to calculate the retardation effects of overload and dwell time.It is observed that the model can reasonably reflect the retardation effects due to compressive plastic zone in the vicinity of the crack tip induced by dwell time.The model can theoretically explain the retardation phenomenon and validation tests will be conducted in the future’s research.

    Acknowledgments

    This work is supported by Youth Foundation of Jiangsu Province‘Study on the time-scale crack growth rate model used in fatigue life assessment of pressure hull of deep-sea submersibles’(Project No.BK2012095);Special program for Hadal Science and Technology of Shanghai Ocean University(Project No.HAST-T-2013-01);The doctoral research fund of Shanghai Ocean University(2013-2015).

    [1]Munz D,Bachmann V.Effect of hold time and environment on fatigue crack growth rate in Ti alloys[J].Material wissenschaft und Werkstofftechnik,1980,11(5):168-172.

    [2]Wakai T,Poussard C,Drubay B.A comparison between Japanese and French A16 defect assessment procedures for creepfatigue crack growth[J].Nuclear Engineering and Design,2003,224(3):245-252.

    [3]Zhao J,Mo T,Nie D F,Ren M F,Guo X L,Chen W X.Acceleration and retardation of fatigue crack growth rate due to room temperature creep at crack tip in a 304 stainless steel[J].Journal of Materials Science,2006,41(19):6431-6434.

    [4]Cui W,Wang F,Huang X.A unified fatigue life prediction method for marine structures[J].Marine Structures,2011,24 (2):153-181.

    [5]Newman J J.A crack opening stress equation for fatigue crack growth[J].International Journal of Fracture,1984,24(4): 131-135.

    [6]Liu Q,Wang F,Huang X P,Cui W C.Three dimensional FE analysis of the plastic zone size near the crack tip[J].Journal of Ship Mechanics,2006,10(5):90-99.

    [7]Voorwald H J C,Torres M A S,Pinto Júnior C C E.Modelling of fatigue crack growth following overloads[J].International Journal of Fatigue,1991,13(5):423-427.

    [8]Dowling N E.Mechanical behavior of materials:engineering methods for deformation,fracture,and fatigue[M].Prentice Hall,1993.

    [9]Wang F,Cui W,Pan B,Shen Y,Huang X.Normalised fatigue and fracture properties of candidate titanium alloys used in the pressure hull of deep manned submersibles[J].Ships and Offshore Structures,(ahead-of-print),2013:1-14.

    U661.4Document code:A

    10.3969/j.issn.1007-7294.2014.09.010

    1007-7294(2014)09-1117-12

    date:2014-04-23

    Supported by Youth Foundation of Jiangsu Province(BK2012095);Special program for Hadal Science and Technology of Shanghai Ocean University(HAST-T-2013-01);The doctoral research fund of Shanghai Ocean University(2013-2015)

    Biography:WANG Fang(1979-),female,Associate researcher of Shanghai Ocean University,E-mail: wangfang@shou.edu.cn;CUI Wei-cheng(1963-),male,professor/tutor.

    欧美精品亚洲一区二区| 日韩熟女老妇一区二区性免费视频| 日本免费在线观看一区| 美女主播在线视频| 伦理电影免费视频| 狂野欧美激情性bbbbbb| 久久国产精品男人的天堂亚洲 | 嘟嘟电影网在线观看| 秋霞伦理黄片| 大香蕉久久网| 亚洲av国产av综合av卡| 免费久久久久久久精品成人欧美视频 | 纯流量卡能插随身wifi吗| 成年女人在线观看亚洲视频| 成人毛片60女人毛片免费| 日本wwww免费看| 国产综合精华液| 国产 精品1| 日日啪夜夜爽| 久久久久久久久久成人| 黄片无遮挡物在线观看| 久久ye,这里只有精品| 亚洲国产色片| 精品亚洲成a人片在线观看| 看免费成人av毛片| 婷婷色综合大香蕉| 嫩草影院新地址| 久久精品国产亚洲网站| 久久精品熟女亚洲av麻豆精品| 免费观看av网站的网址| 午夜激情久久久久久久| 一本一本综合久久| 少妇精品久久久久久久| 大话2 男鬼变身卡| 国产男女内射视频| 亚洲精品成人av观看孕妇| a级一级毛片免费在线观看| 亚洲av日韩在线播放| 色吧在线观看| 一区二区三区免费毛片| 久久久a久久爽久久v久久| 国产av精品麻豆| 草草在线视频免费看| 久久 成人 亚洲| 免费看日本二区| 亚洲,欧美,日韩| 国产精品偷伦视频观看了| 中国国产av一级| 在线免费观看不下载黄p国产| 精品一品国产午夜福利视频| 精品人妻偷拍中文字幕| 成人18禁高潮啪啪吃奶动态图 | 老熟女久久久| 欧美最新免费一区二区三区| 日本vs欧美在线观看视频 | 亚洲av二区三区四区| 日韩中字成人| 久久久久久久精品精品| 久久久久久人妻| 女人久久www免费人成看片| 免费观看a级毛片全部| 在线观看美女被高潮喷水网站| 麻豆精品久久久久久蜜桃| 国产精品不卡视频一区二区| 午夜av观看不卡| 天堂8中文在线网| 免费在线观看成人毛片| 日韩,欧美,国产一区二区三区| 日韩av在线免费看完整版不卡| 午夜久久久在线观看| 亚洲国产精品成人久久小说| 中国美白少妇内射xxxbb| 亚洲一区二区三区欧美精品| 精品少妇久久久久久888优播| 麻豆精品久久久久久蜜桃| 国产毛片在线视频| 又大又黄又爽视频免费| 大片免费播放器 马上看| 亚洲国产精品国产精品| 国产免费福利视频在线观看| 男女国产视频网站| 香蕉精品网在线| 一个人看视频在线观看www免费| 黄片无遮挡物在线观看| 18禁在线无遮挡免费观看视频| 蜜桃久久精品国产亚洲av| 黄色配什么色好看| 亚洲伊人久久精品综合| 中文乱码字字幕精品一区二区三区| 青春草视频在线免费观看| 天天操日日干夜夜撸| 国产国拍精品亚洲av在线观看| 五月天丁香电影| 日韩电影二区| 久久免费观看电影| 国产高清有码在线观看视频| 老女人水多毛片| 精品熟女少妇av免费看| 国产精品一区二区在线不卡| 超碰97精品在线观看| 伊人久久精品亚洲午夜| 最黄视频免费看| 国产免费视频播放在线视频| 丝瓜视频免费看黄片| 欧美日韩综合久久久久久| 我的女老师完整版在线观看| 热99国产精品久久久久久7| 久久婷婷青草| 午夜日本视频在线| 91精品国产国语对白视频| 丝瓜视频免费看黄片| 高清午夜精品一区二区三区| av天堂久久9| 日本黄色片子视频| av天堂中文字幕网| 亚洲欧洲日产国产| 少妇熟女欧美另类| 国产欧美亚洲国产| 亚洲欧洲国产日韩| 亚洲欧美中文字幕日韩二区| 成年人免费黄色播放视频 | 在线观看www视频免费| 国产探花极品一区二区| 日韩大片免费观看网站| 日韩亚洲欧美综合| 久久久久久久久久成人| 丰满人妻一区二区三区视频av| 国产精品久久久久成人av| 国产淫语在线视频| 婷婷色综合大香蕉| 插阴视频在线观看视频| 亚洲人成网站在线观看播放| 少妇人妻 视频| 亚洲国产最新在线播放| 男人添女人高潮全过程视频| 亚洲天堂av无毛| videossex国产| 日本欧美视频一区| 91aial.com中文字幕在线观看| 国产黄片视频在线免费观看| 国产高清三级在线| 亚洲av欧美aⅴ国产| 久久影院123| 晚上一个人看的免费电影| 国产精品一区二区在线观看99| 各种免费的搞黄视频| 欧美精品亚洲一区二区| 亚洲成色77777| 国产男人的电影天堂91| 人妻少妇偷人精品九色| 久久精品国产亚洲av涩爱| 精品一区二区免费观看| 99热这里只有是精品在线观看| 亚洲中文av在线| 97超视频在线观看视频| 成人二区视频| 大陆偷拍与自拍| 七月丁香在线播放| 日韩 亚洲 欧美在线| 日日摸夜夜添夜夜添av毛片| 日韩中字成人| 国内精品宾馆在线| 看免费成人av毛片| 欧美另类一区| 丝袜在线中文字幕| 99精国产麻豆久久婷婷| 久久人人爽av亚洲精品天堂| 国产一区有黄有色的免费视频| 91午夜精品亚洲一区二区三区| 人人澡人人妻人| 亚洲国产精品国产精品| 久久99蜜桃精品久久| 美女福利国产在线| 欧美老熟妇乱子伦牲交| 亚洲美女视频黄频| 少妇 在线观看| 亚洲国产日韩一区二区| 啦啦啦在线观看免费高清www| 久久精品国产亚洲网站| 一级毛片黄色毛片免费观看视频| 亚洲精品国产成人久久av| 少妇人妻精品综合一区二区| 国产亚洲av片在线观看秒播厂| 一级毛片aaaaaa免费看小| 色网站视频免费| 少妇被粗大猛烈的视频| 黄色怎么调成土黄色| 一级黄片播放器| 在线观看免费视频网站a站| 久久人妻熟女aⅴ| 一级毛片 在线播放| 国产精品久久久久久av不卡| 国产亚洲一区二区精品| 欧美日本中文国产一区发布| av福利片在线| 国产精品一区二区在线不卡| 国产成人aa在线观看| 在线观看一区二区三区激情| .国产精品久久| 亚洲欧洲国产日韩| 久久青草综合色| 久久精品久久久久久久性| 人妻一区二区av| 街头女战士在线观看网站| 午夜老司机福利剧场| 日韩在线高清观看一区二区三区| 亚洲av福利一区| 热re99久久精品国产66热6| 久久久久久久久久人人人人人人| 18禁在线播放成人免费| 亚洲三级黄色毛片| 搡女人真爽免费视频火全软件| 精品人妻熟女av久视频| 欧美区成人在线视频| 男女国产视频网站| 涩涩av久久男人的天堂| 久久国产乱子免费精品| 最近2019中文字幕mv第一页| 99精国产麻豆久久婷婷| 中文字幕av电影在线播放| 日韩电影二区| 国产极品粉嫩免费观看在线 | 91精品国产九色| 亚洲欧美精品自产自拍| 国产精品久久久久久av不卡| 免费看不卡的av| 久久久久久久久大av| 国产视频内射| 免费观看在线日韩| 精品卡一卡二卡四卡免费| 国产在线男女| 久久久久久久久大av| 性色av一级| 日本黄大片高清| 免费观看无遮挡的男女| 欧美人与善性xxx| 国产欧美另类精品又又久久亚洲欧美| 妹子高潮喷水视频| 亚洲精品日韩在线中文字幕| 日本欧美国产在线视频| 女人久久www免费人成看片| 欧美少妇被猛烈插入视频| av黄色大香蕉| av播播在线观看一区| 99久久精品国产国产毛片| 久久久久国产网址| 青青草视频在线视频观看| 久久国产精品男人的天堂亚洲 | 国产午夜精品久久久久久一区二区三区| 国语对白做爰xxxⅹ性视频网站| 午夜免费男女啪啪视频观看| 一级片'在线观看视频| 国产爽快片一区二区三区| 婷婷色麻豆天堂久久| 成人无遮挡网站| 亚洲无线观看免费| 国产亚洲午夜精品一区二区久久| 少妇精品久久久久久久| 久久久久久伊人网av| 成人二区视频| 日韩av不卡免费在线播放| 亚洲va在线va天堂va国产| 不卡视频在线观看欧美| 丰满迷人的少妇在线观看| 日韩视频在线欧美| 日日撸夜夜添| 亚洲av综合色区一区| 美女大奶头黄色视频| videossex国产| 中文字幕亚洲精品专区| 日日啪夜夜撸| 老司机亚洲免费影院| 人人妻人人澡人人爽人人夜夜| 青春草亚洲视频在线观看| 夜夜爽夜夜爽视频| 国产精品国产三级国产av玫瑰| 在线免费观看不下载黄p国产| 国产伦理片在线播放av一区| 日本色播在线视频| 一区二区三区四区激情视频| 国产亚洲av片在线观看秒播厂| 22中文网久久字幕| 97超视频在线观看视频| 高清欧美精品videossex| 日本91视频免费播放| 寂寞人妻少妇视频99o| 国产亚洲欧美精品永久| 国产精品嫩草影院av在线观看| 成年女人在线观看亚洲视频| 亚洲精品自拍成人| 自拍欧美九色日韩亚洲蝌蚪91 | 亚洲av日韩在线播放| 夜夜看夜夜爽夜夜摸| 国产精品欧美亚洲77777| 国产亚洲av片在线观看秒播厂| av福利片在线| 国产69精品久久久久777片| 永久网站在线| 嫩草影院入口| 日本黄色日本黄色录像| 视频中文字幕在线观看| 日韩成人伦理影院| 免费av中文字幕在线| 日日啪夜夜爽| 国产精品99久久久久久久久| 久久久久人妻精品一区果冻| 亚洲精品乱码久久久v下载方式| 久久久久国产网址| 成年美女黄网站色视频大全免费 | 久久久a久久爽久久v久久| 亚洲精品乱码久久久久久按摩| 最近中文字幕高清免费大全6| 亚洲国产毛片av蜜桃av| 国产亚洲5aaaaa淫片| 成年人午夜在线观看视频| 亚洲精品一二三| 我的女老师完整版在线观看| 久久精品国产a三级三级三级| 国产毛片在线视频| 国产成人freesex在线| 久久99热6这里只有精品| 少妇 在线观看| 亚洲人与动物交配视频| 秋霞在线观看毛片| 伊人久久国产一区二区| 一个人看视频在线观看www免费| 成人亚洲精品一区在线观看| 男女无遮挡免费网站观看| 高清午夜精品一区二区三区| 一级毛片 在线播放| 午夜福利影视在线免费观看| 久久久a久久爽久久v久久| 国产免费福利视频在线观看| 啦啦啦在线观看免费高清www| 国产老妇伦熟女老妇高清| 亚洲三级黄色毛片| 亚洲精品aⅴ在线观看| 午夜久久久在线观看| 亚洲欧美一区二区三区国产| 欧美高清成人免费视频www| 日产精品乱码卡一卡2卡三| 国产视频首页在线观看| 亚洲精品第二区| 亚洲无线观看免费| 国产精品成人在线| 久久99热这里只频精品6学生| 国产一级毛片在线| 性高湖久久久久久久久免费观看| 日本wwww免费看| 日韩免费高清中文字幕av| 男女无遮挡免费网站观看| 亚洲精品视频女| 9色porny在线观看| 晚上一个人看的免费电影| 精品国产露脸久久av麻豆| 有码 亚洲区| 丰满饥渴人妻一区二区三| 人妻制服诱惑在线中文字幕| 少妇人妻久久综合中文| 成年人午夜在线观看视频| 精品人妻熟女毛片av久久网站| 99热国产这里只有精品6| 精品国产国语对白av| 伊人久久国产一区二区| 欧美xxⅹ黑人| 国产亚洲欧美精品永久| 亚洲精品第二区| 岛国毛片在线播放| 丰满人妻一区二区三区视频av| 人妻人人澡人人爽人人| 久久狼人影院| 日产精品乱码卡一卡2卡三| 日本爱情动作片www.在线观看| 亚洲美女搞黄在线观看| 全区人妻精品视频| 一边亲一边摸免费视频| 国产精品久久久久久精品电影小说| 久热这里只有精品99| 国产黄频视频在线观看| 啦啦啦视频在线资源免费观看| 乱人伦中国视频| 制服丝袜香蕉在线| av一本久久久久| 久久久久久久大尺度免费视频| 黄色日韩在线| 国产成人精品婷婷| 超碰97精品在线观看| 三级经典国产精品| 大码成人一级视频| 99热全是精品| 女人久久www免费人成看片| 亚洲一级一片aⅴ在线观看| 熟女人妻精品中文字幕| 午夜免费鲁丝| 成年av动漫网址| 亚洲欧美精品自产自拍| 国产精品免费大片| 热re99久久精品国产66热6| 国产一区二区三区综合在线观看 | 久久久久网色| 丁香六月天网| 男女啪啪激烈高潮av片| 国产高清有码在线观看视频| 日本91视频免费播放| 国产黄色免费在线视频| 国产免费视频播放在线视频| 在线观看一区二区三区激情| 日产精品乱码卡一卡2卡三| 热re99久久国产66热| 国产淫语在线视频| 国产 一区精品| 一本久久精品| 亚洲国产精品999| 国内揄拍国产精品人妻在线| 国内精品宾馆在线| 日韩成人伦理影院| 亚洲怡红院男人天堂| 亚洲国产精品成人久久小说| 伦精品一区二区三区| 七月丁香在线播放| 韩国av在线不卡| h日本视频在线播放| 久久人人爽人人爽人人片va| 欧美3d第一页| 熟女电影av网| 18禁在线播放成人免费| 精品人妻一区二区三区麻豆| 国产极品天堂在线| 日韩欧美精品免费久久| 亚洲精品一二三| 97超视频在线观看视频| 青春草国产在线视频| 夫妻性生交免费视频一级片| 多毛熟女@视频| 熟妇人妻不卡中文字幕| 日韩av不卡免费在线播放| 亚洲成人手机| 亚洲人成网站在线观看播放| 日韩不卡一区二区三区视频在线| 成年人午夜在线观看视频| 久久久久国产网址| 男女边吃奶边做爰视频| 久久久久久久大尺度免费视频| 交换朋友夫妻互换小说| 亚洲色图综合在线观看| 精品一区二区三卡| 大又大粗又爽又黄少妇毛片口| 久久久久久久久大av| 99热这里只有是精品在线观看| 肉色欧美久久久久久久蜜桃| 久久6这里有精品| 国产日韩欧美在线精品| 日韩av在线免费看完整版不卡| 国产成人免费无遮挡视频| 国产欧美另类精品又又久久亚洲欧美| 精品国产国语对白av| 丝袜喷水一区| 日韩成人伦理影院| 美女大奶头黄色视频| 国产免费视频播放在线视频| 赤兔流量卡办理| 国产成人91sexporn| 青春草国产在线视频| 日本-黄色视频高清免费观看| 视频中文字幕在线观看| 99热这里只有是精品50| 在线观看免费日韩欧美大片 | 午夜免费鲁丝| 久久这里有精品视频免费| 久久久久久久久大av| 少妇丰满av| 国产精品熟女久久久久浪| 人妻制服诱惑在线中文字幕| 久久久久人妻精品一区果冻| 久热这里只有精品99| 国产亚洲午夜精品一区二区久久| 午夜影院在线不卡| 九九久久精品国产亚洲av麻豆| 嘟嘟电影网在线观看| 欧美亚洲 丝袜 人妻 在线| 国产 精品1| 天天操日日干夜夜撸| 色婷婷久久久亚洲欧美| 精品国产一区二区三区久久久樱花| 卡戴珊不雅视频在线播放| 男人添女人高潮全过程视频| 99久久中文字幕三级久久日本| 成年av动漫网址| 精品国产乱码久久久久久小说| 在线观看www视频免费| 这个男人来自地球电影免费观看 | 各种免费的搞黄视频| 精品亚洲乱码少妇综合久久| 亚洲欧洲国产日韩| 国产精品蜜桃在线观看| 街头女战士在线观看网站| 一级黄片播放器| 久久久亚洲精品成人影院| 国产老妇伦熟女老妇高清| 寂寞人妻少妇视频99o| 亚洲综合精品二区| av天堂中文字幕网| 91精品伊人久久大香线蕉| 欧美激情极品国产一区二区三区 | 久久久午夜欧美精品| 国产成人aa在线观看| 午夜福利网站1000一区二区三区| 免费观看的影片在线观看| 人体艺术视频欧美日本| 亚洲婷婷狠狠爱综合网| 国产高清不卡午夜福利| 精品少妇内射三级| 女人久久www免费人成看片| 亚洲,一卡二卡三卡| 精品少妇黑人巨大在线播放| 日韩强制内射视频| 亚洲人成网站在线观看播放| 91久久精品国产一区二区三区| 久热这里只有精品99| 激情五月婷婷亚洲| 另类亚洲欧美激情| 女人精品久久久久毛片| 欧美 日韩 精品 国产| 免费播放大片免费观看视频在线观看| 晚上一个人看的免费电影| 少妇被粗大猛烈的视频| 丝袜在线中文字幕| 成人黄色视频免费在线看| 免费看av在线观看网站| 五月伊人婷婷丁香| 女的被弄到高潮叫床怎么办| 美女主播在线视频| 亚洲av不卡在线观看| 少妇被粗大猛烈的视频| 亚洲国产色片| 自线自在国产av| 深夜a级毛片| 另类精品久久| 91aial.com中文字幕在线观看| 性色avwww在线观看| 亚洲成人av在线免费| 国产亚洲最大av| 少妇熟女欧美另类| 亚洲av国产av综合av卡| a 毛片基地| 日韩人妻高清精品专区| 麻豆成人午夜福利视频| 91午夜精品亚洲一区二区三区| a 毛片基地| 日韩av在线免费看完整版不卡| 一级黄片播放器| 亚洲美女黄色视频免费看| 亚洲国产欧美日韩在线播放 | 亚洲国产精品成人久久小说| 男女啪啪激烈高潮av片| 韩国高清视频一区二区三区| 少妇被粗大猛烈的视频| 乱人伦中国视频| 大码成人一级视频| 国产淫语在线视频| 一级a做视频免费观看| 99久久精品一区二区三区| 久久午夜综合久久蜜桃| 久久久久国产网址| 国模一区二区三区四区视频| 波野结衣二区三区在线| 欧美日韩国产mv在线观看视频| 人体艺术视频欧美日本| 精品一区二区三区视频在线| 久久热精品热| 妹子高潮喷水视频| 日韩不卡一区二区三区视频在线| 一个人免费看片子| 免费久久久久久久精品成人欧美视频 | 久久久久久久国产电影| 搡女人真爽免费视频火全软件| 国产色爽女视频免费观看| 又粗又硬又长又爽又黄的视频| 两个人免费观看高清视频 | 精品少妇黑人巨大在线播放| 亚洲综合精品二区| 久久久亚洲精品成人影院| 另类精品久久| 草草在线视频免费看| videos熟女内射| 少妇的逼好多水| 伦精品一区二区三区| 在线观看国产h片| 老司机亚洲免费影院| 日本免费在线观看一区| 性色avwww在线观看| 高清黄色对白视频在线免费看 | 久久鲁丝午夜福利片| 最后的刺客免费高清国语| 天堂中文最新版在线下载| 曰老女人黄片| 只有这里有精品99| 亚洲av不卡在线观看| 免费不卡的大黄色大毛片视频在线观看| 日韩欧美一区视频在线观看 | 人妻一区二区av| 黄色毛片三级朝国网站 | 日韩免费高清中文字幕av| 在线观看av片永久免费下载| 国产69精品久久久久777片| 91午夜精品亚洲一区二区三区| 亚洲欧美中文字幕日韩二区| 一级,二级,三级黄色视频| 香蕉精品网在线| 久久99蜜桃精品久久| 日韩一区二区三区影片| av免费观看日本| 久久久a久久爽久久v久久| 噜噜噜噜噜久久久久久91| 欧美日本中文国产一区发布|