• <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 ?

    Effects of process parameters on mechanical properties of abrasive-assisted electroforming nickel

    2016-11-24 00:49:30RenJianhuaZhuZengweiZhuDi
    CHINESE JOURNAL OF AERONAUTICS 2016年4期

    Ren Jianhua,Zhu Zengwei,Zhu Di

    College of Mechanical and Electrical Engineering,Nanjing University of Aeronautics and Astronautics,Nanjing 210016,China

    Effects of process parameters on mechanical properties of abrasive-assisted electroforming nickel

    Ren Jianhua,Zhu Zengwei*,Zhu Di

    College of Mechanical and Electrical Engineering,Nanjing University of Aeronautics and Astronautics,Nanjing 210016,China

    A cathode mandrel with translational and rotational motion,which was supposed to obtain uniform friction effect on surface,was employed in abrasive-assisted electroforming for revolving parts with complex profile.The effects of current density,translational speed and rotational speed on the deposit properties were studied by orthogonal test.The tensile strength,elongation and micro hardness value were measured to find out how the factors affected the properties.The optimized results show that changes of current density affect the tensile strength of nickel layer most,while translational speed has the most remarkable influences on both elongation and micro hardness.The low rotational speed affects the properties least.In this experiment,a smooth nickel layer with tensile strength 581 MPa,elongation 17%and micro hardness 248HV is obtained by the orthogonal test.

    1.Introduction

    Metallic thin-wall parts of complex surface manufactured by electroforming are heavily required by modern industry, for electroforming is a precision manufacture technology or by far the most efficient way to produce these parts.By employing the principle of electrodeposition,electroforming can copy microscopic detail,reproduce accurate dimensions,and form components of controllable material property for desirablefunctions in applications such as precision mould,shaped charge liner,cryogenic upper stage main engine,1–5etc.

    However,the applications of traditional electroforming process always go with some drawbacks at the electroforming layer, for example,pinholes and nodules on the surface,coarse grain size and long electroforming cycle.So far,a majority of researchers have been engaged in various kinds of additives,some of which could really reduce the grain size and enhance the strength of the deposits in electroforming process,and others could eliminate the pits and make the deposited layer surface smooth.6,7However,it is difficult to maintain the electrolyte baths because the additive agents are consumed during the electrodeposited process by decomposition and being absorbed on the cathode which leads to code position of sulfur and carbon.8,9Researchers have blamed the high-temperature ductility losses in nickel on sulfur and carbon that are supposed to give rise to the embrittlement of deposits.10

    Studies made by researchers have shown that abrasiveassisted nick elelectroforming process could effectively eliminate pinholes,remove nodules,positively affect crystal nucleation,and refine the grains of layer,and thus nearmirror electroforming layer was obtained without any organic additives.11,12

    Generally speaking,there are two independent cathode motions in the abrasive-assisted electroforming process to obtain friction effect on cathode surface.A pure rotational motion was designed for revolving parts electroforming,and a designed translational cathode in horizontal type was employed in complex shaped non-rotating parts electroforming.However, for revolving parts with complex surface in abrasive-assisted nickel electroforming process,neither of the two single cathode motions would be carried out.Firstly,there are different linear velocities along the axial direction of cathode because of diverse curvature radius in pure rotational motion.Secondly,the varying electric field intensity on cathode surface for pure translational motion should be taken into consideration because it will lead to the nonuniformity in thickness of deposits.Naturally,the friction effect would also be inhomogeneous.To solve the problems mentioned above,a horizontally positioned cathode with complicated movement in combination of translation and rotation is proposed in this paper.The complex effects of current density,translational speed and rotational speed on the deposit microstructure and properties were studied by orthogonal test.The tensile strength,elongation and micro hardness values were also measured.

    2.Principle and experiments

    Fig.1 shows the scheme of experimental principle of abrasive assisted electro forming process with moving cathode.n1and n2are the rotation directions of ceramic beads.V is translational speed.V′is rotational speed.A cylinder mandrel is translated as well as rotated in horizontal type.In the nickel electr ofoZrming process,nonconductive hydrogen bubbles usually adhere to cathode surface impeding nickel ion deposition.The free ceramic beads filling in the space between cathode and anode were forced to polish the growing deposited layer slightly and uniformly,driving the hydrogen bubbles away,during the electroforming process.13,14The rotation of cathode was set at low speed,while the translational speed was set much higher and played the key role in driving the beads.The orbital movement of cathode mandrel was a circle.The reasons are presented below.11,12On one hand,different parts of the cathode have the same linear velocity during the cathode’s translation to make sure the polishing effect on the whole surface in uniformity.On the other hand,the rotation of cathode could maintain the cathode surface in the same electric field intensity,and achieve uniform polishing effect on circumference surface.

    Fig.2 illustrates the schematic diagram of the experimental apparatus.The cathode’s translational movement was carried out by a planar worktable driven by stepper motor in X/Y axis linkage.And a speed control motor was employed to drive the rotation of the cathode via transmission mechanism.Nickel pellets were used as anode.A stainless steel cylinder mandrel was used as cathode in horizontal type whose deposit area was ?70 mm × 100 mm.Free ceramic beads in 0.8–1.2 mm diameter were chosen as the abrasive medium filling the space between the electrodes to maintain continuous friction on the cathode’s surface in the process of electroforming.The electrolyte was pumped from the storage bath to the electroforming unit and flowed through the gap between cathode and anode.Both the electrolyteflushing and the moving cathode motion served as the agitation of the electrolyte.The electrolyte’s temperature was controlled by a heater and temperature controller.Be fore deposition,the cathode was mechanically polished,degreased with organic solvent,and rinsed with ethanol.

    Fig.1 Scheme of experimental principle of abrasive-assisted electroforming process with moving cathode.

    Fig.2 Schematic diagram of experimental apparatus.

    An orthogonal method was used to study the effects of the three factors:current density(A),translational speed(B)and rotational speed(C)on the mechanical properties of nickel layers,and each factor had three levels.Thus,the variable factors and levels formed an orthogonal array(Tables 1 and 2).A L9 orthogonal array was selected for optimization of the process parameters.15,16

    All solutions were prepared by deionized water and analytical reagents were used.No additive was used.The solution content and the experiment condition are shown in Table 3.At the end of the process,the cathode was immediately withdrawn,rinsed with deionized water,dried and then detected.

    A HITACHI S3400N SEM was used to observe the surface morphology of the samples.A HXS-1000A Vickers micro hardness tester was used to measure the micro hardness of the nickel deposits at room temperature.A load of 0.49 N was applied and kept for 15 s.Thefinal value quoted for the hardness of each deposit is the average of six times.A Instron 5566 tensile strength tester was used to measure the strength property,the thickness of the samples was kept at about 0.7 mm by controlling the current density and deposition time,and the tensile rate was kept at 0.2 mm/min.

    3.Results and discussions

    As Fig.3(a)shows,there are distinct groove marks on the surface of nickel deposit with purely rotating cathode in a very long electroforming cycle,while Fig.3(b)shows smoothsurface of nickel deposit with complicated moving cathode.The linear speed in Fig.3(a)is a little higher than that in Fig.3(b),so the surface in Fig.3(a)is brighter than Fig.3(b).17,18There is no doubt that the friction effect of ceramic beads with ordinary rotating cathode is too strong to obtain smooth-surfaced deposit layer when the cathode linear speed is at about 20–100 mm/s.The marks on the surface are just the same as the purely rotational movement of cathode.However,when a complicated moving cathode was employed,the ceramic beads were forced to move in a complicated way,achieving uniform polishing effect on circumference surface.

    Table 1 Orthogonal factors and levels.

    Table 2 L9 orthogonal array.

    Table 3 Bath composition and process conditions of nickel electroforming.

    Then the results of orthogonal test are shown in Table 4,among which I,II,III show the average value of each factor under different levels respectively.The range value in Table 4 shows the degree of the effect of factors on mechanical properties;the maximum value is written in bold;the larger the value is,the more significant the effect is.Table 4 shows the tensile strength,elongation and micro hardness values of each orthogonal array group.As can be seen from Table 4,the factors influencing tensile strength arranged by the order from major to minor are current density,translational speed,and rotational speed,namely A,B,and C.In addition,the influence of current density is the most significant,and translational speed is the second.As to influence on elongation,translational speed is the most significant factor,current density is the second,and rotational speed is the last,namely B,A,and C.There is no significant difference between the first two factors.The factors with their influence on micro hardness listed from the most to the least important are translational speed,current density,and rotational speed,namely B,A,and C,and also the significance levels of first two factors are nearly equal.

    The effects of current density,translational speed and rotational speed on the properties of nickel deposits are discussed as follows.

    Fig.3 Abrasive-assisted nickel electroforming process when deposit grows thick at current density of 3 A/dm2.

    Table 4 Tensile strength,elongation and micro hardness of electroformed nickel orthogonal array.

    3.1.Effects of process parameters on tensile strength of nickel deposits

    Fig.4 shows the effect of each factor on tensile strength of electroformed nickel with moving cathode that is obtained from the results of Table 4.As Fig.4(a)presents,tensile strength value of nickel electroformed decreases at first,and then rises when current density increases from 2 A/dm2to 6 A/dm2.There is a big fluctuation in the tensile strength values with the increase of current density.At the same time,there is a quick increase of tensile strength value with the increase of translational speed,as plotted in Fig.4(b).In addition,there is a positive correlation between tensile strength and rotational speed in Fig.4(c).It seems that current density is the most significant factor influencing the variation of tensile strength,either increase or decrease.However,the translational speed might be another significantly positive factor to increase the tensile strength.As shown in Fig.5,when the moving speed of cathode increases,the abrasion strength becomes more distinguishable and grains grow smaller where current density stays the same.When the cathode speed increases,the polishing can be strengthened and help to obtain smooth nickel layers with fine mechanical properties by increasing the activated points on cathode and refine the grain size.Thus,the tensile strength increases with increasing translational speed as well as rotational speed because there is a negative correlation between tensile strength and grain size.The rotational speed is so low that it can be supposed to have uniform abrasion effect on revolving parts with complicated profiles and maintain the circumference surface in the same electric field intensity.

    Fig.4 Effect of each factor on tensile strength of electroformed nickel.

    Fig.5 Effect of moving speed on SEM morphology of electroforming nickel with increasing translational speed and rotational speed at the same current density(No.1,2,3 from orthogonal array of Table 2).

    Fig.6 Effect of current density on SEM morphology of electroformed nickel with the same translational speed but increasing rotational speed(No.1,4,7 from orthogonal array of Table 2).

    As shown from Fig.6,higher current density may lead to coarser crystal grains and loose structure.When current density increases,the abrasion effect is not really obvious and the grains grow bigger.So the SEM Simages are the evidence that low tensile strength can be sourced in coarse crystal grains and loose structure.Tensile strength of 4 A/dm2is lower than that of 6 A/dm2in Fig.4(a)maybe because the moving speed at 6 A/dm2is higher than that at 4 A/dm2.The tensile strength is strengthened by the free beads’polishing effect.The influence of current density on property of electroforming nickel is remarkable.Hence, for obtaining nickel layer with proper property,the current density requires tight control for slight change in it will cause much change in tensile strength.

    3.2.Effects of process parameters on elongation of nickel deposits

    Fig.7 shows the effect of each factor on elongation of electroformed nickel with moving cathode that is obtained from the results of Table 4.As plotted in Fig.7(a),the elongation of electroformed nickel first goes up,and then goes down with current density increasing from 2 A/dm2to 6 A/dm2,just contrary to the influence on tensile strength in Fig.4(a).As shown in Fig.6,higher current density may lead to coarser crystal grains and loose structure.When tensile strength goes low,the elongation will increase.Data on the effect of current density show that a 4 A/dm2current density should be used for good elongation and high tensile strength.

    When translational speed increases,the dominant trend of effect on deposits is a quick decrease of the elongation in Fig.7(b).The influence of translational speed on elongation of electroforming nickel is remarkable.As shown in Figs.4 and 5,faster translational speed may lead to higher tensile strength,and the corresponding elongation gets lower.Hence, for obtaining nickel layer with proper property,the translational speed requires tight control because slight change in it will cause much change in elongation.

    In Fig.7(c),there is a small positive and then a small negative correlation between elongation and rotational speed.Data on the effect of rotational speed are so small that the rotational speed has really loose correlation with elongation.Well,the rotational speed at low range is supposed to have uniform abrasion effect.The rotational speed should be controlled low enough to get higher elongation.

    3.3.Effects of process parameters on micro hardness of nickel deposits

    Fig.7 Effect of each factor on elongation of electroforming nickel.

    Fig.8 Effect of each factor on micro hardness of electroforming nickel.

    As Fig.8(a)presents,micro hardness values of electroformed nickel decrease at first,and then rise when current density increases from 2 A/dm2to 6 A/dm2.But there is a downward trend overall.In Fig.8(b),the dominant trend is a quick increase of micro hardness value of electroforming nickel with the increase of translational speed.Generally,hardness has the same effect tendency as tensile strength does.And there is a negative correlation between tensile strength and grain size.So the higher hardness might be attributed to the compact and fine-grained deposit structure.There is a small negative correlation between micro hardness and rotational speed in Fig.8(c).The effect of rotational speed is non-significant and negligible.

    3.4.Process parameters optimization procedure

    The optimization analysis process by overall equilibrium of the properties19,20is shown as follows.

    As Table 4,Figs.3,6 and 7 show,translational speed has the most remarkable influences both on elongation and micro hardness.Level 20 mm/s is good in factor B in view of relatively high elongation value.To tensile strength,the influence of translational speed is not the largest,so level 20 mm/s is also the best.

    Rotational speed is not a remarkable influence to any of the three properties.As shown in Figs.3,6 and 7,level 1 r/min is good in factor C in view of tensile strength and elongation.Furthermore,level 1 r/min in factor C is not the lowest to micro hardness,so level 1 r/min is the best in factor C.

    Current density is the most remarkable influencefactor to tensile strength as shown in Table 4.Fig.3(a)shows that level 2 A/dm2is the best in factor A,and 6 A/dm2is the second.But level 6 A/dm2is better to elongation and it is not the lowest to micro hardness.Thus,level 6 A/dm2is the best in factor A.

    4.Conclusions

    (1)An orthogonal test of abrasive-assisted nickel electroforming process was carried out with moving cathode in combination of translation and rotation.The influences of current density,translational speed and rotational speed on the microstructure and properties of deposits were studied.

    (2)In order to realize high-speed nickel electroforming by using high current density,faster translational speed should be applied to obtain higher mechanical properties,such as tensile strength and micro hardness.

    (3)To achieve uniform friction effect on deposits for the abrasive-assisted electroforming of revolving parts with complex surface profile,both translational and rotational motion are necessary.For most of the friction effects were attributed to translational cathode,the rotation could achieve uniform polishing effect at circumferential direction of cathode surface and maintain the surface in the same electric field intensity.

    (4)Changes of current density affected the tensile strength of nickel layer most,while translational speed had the most remarkable influences both on elongation and micro hardness.Slow rotational speed had the smallest influence on properties of deposits.In this experiment,best factors with A3B2C2(6 A/dm2,20 mm/s,1 r/min)were obtained by using the optimized analysis:overall equilibrium of the properties.A smooth nickel layer with comprehensive propertiesof tensile strength 581 MPa,elongation 17%and micro hardness 248HV was obtained.

    Acknowledgement

    Authors acknowledge financial support from the Program for New Century Excellent Talents in University of China(No.NCET-10-0074).

    1.Brousseau EB,Dimov SS,Pham DT.Some recent advances in multi-material micro-and nano-manufacturing.Int J Adv Manuf Technol 2010;47(1–4):161–80.

    2.Qu NS,Qian WH,Hu XY,Zhu ZW.Preparation of a microprism Ni-Ceo2 nanocomposite mold by electroforming.Mater Manuf Processes 2014;29(1):37–41.

    3.Huang MS,Ku HH.Microinjection molding of light-guided plates using LIGA-likefabricated stampers.J Appl Polym Sci 2011;122(5):3446–55.

    4.Larson C,Smith JR.Recent trends in metal alloy electrolytic and electrolessplating research:a review.TransIMF 2011;89(6):333–41.

    5.Zhong ZW.Recent advances in polishing of advanced materials.Mater Manuf Processes 2008;23(5):449–56.

    6.Oliveira EM,Finazzi GA,Carlos IA.Influence of glycerol,mannitol and sorbitol on electrodeposition of nickel from a Watts bath and on the nickel film morphology.Surf Coat Technol 2006;200(20):5978–85.

    7.Stoychev D,Vitanova I,Buyukliev R,Petkova N,Popova I,Pojarliev I.Effect of the structure of aromatic disulphides on some physico-mechanical properties of electrodeposited copper coatings.J Appl Electrochem 1992;22(10):987–90.

    8.Dini JW,Johnson HR,Saxton HJ.Influence of sulfur content on the impact strength of electroforming nickel.Electrodeposition Surf Treat 1974;2(3):165–76.

    9.Dini JW,Johnson HR.Electroforming of a throat nozzle for a combustion facility.Plat Surf Finish 1977;64(8):44–51.

    10.Dini JW,Johnson HR.High-temperature ductility of electrodeposited nickel.Sandia Laboratories;1977 Aug.Report No.:SAND 77–8020.

    11.Zhu ZW,Zhu D,Qu NS,Wang K,Yang JM.Electroforming of revolving parts with near-polished surface and uniform thickness.Int J Adv Manuf Technol 2008;39(11–12):1164–70.

    12.Li XL,Zhu ZW,Zhu D,Zhang Y.Orbital-abrasion-assisted electroforming of non-rotating parts.J Wuhan Univ Technol Mater 2011;26(5):827–31.

    13.Watanabe T.Nanoplating–microstructure formation theory of plated films and a database of plated films.Nano plating–microstructure formation theory of plated films and a database of plated films.Elsevier Science;2004.p.118–56.

    14.Zhu D,Zhu ZW,Qu NS.Abrasive polishing assisted nickel electroforming process.CIRP AnnManufTechnol2006;55(7):193–6.

    15.Zhao F,Zhu D,Xue YJ,Zhang WF.Effects of process parameters on composite electrodeposition of Ni-nano-La2O3.Surf Technol 2004;33(2):52–4[Chinese].

    16.Surekar SH,Bhatwadekar SG,Kharche WG,Bilgi DS.Determination of principle component affecting material removal rate in electrochemical machining process.IntJEngSciTechnol 2012;4:2402–8.

    17.Zhu ZW,Zhu D,Qu NS,Lei W.Electrodeposition of bright nickel coating under perturbation of hard particles.Mater Des 2007;28(6):1776–9.

    18.Zhang Y,Zhu ZW,Zhu D.Effect of attrition on mechanical properties of electroforming nickel.Chin J Nonferrous Metals 2012;22(5):1377–82[Chinese].

    19.Montgomery DC.Design and analysis of experiments.New York:John Wileyamp;Sons;2008.p.4–50.

    20.Yu Q,Zeng Y,Xu K,Qu NS,Zhu D.Research on anode vibration and wire electrode travelling in micro wire electrochemical machining.China Mech Eng 2014;25(3):295–9[Chinese].

    REN Jianhua is currently a Ph.D.candidate at College of Mechanical and Electrical Engineering,Nanjing University of Aeronautics and Astronautics.His research interests include electrochemical machining,electroforming,and micro-electrochemical machining.

    ZHU Zengwei is currently a prof essor in Nanjing University of Aeronautics and Astronautics.His research interests include electrochemicalmachining,electroforming,and micro-electrochemical machining.

    ZHU Di is currently a prof essor in Nanjing University of Aeronautics and Astronautics.His research interests include electrochemical machining,electroforming,and micro-electrochemical machining.

    11 January 2016;revised 16 February 2016;accepted 28 March 2016

    Available online 22 June 2016

    Abrasive;

    Cathode compound motion;Electroforming;

    Mechanical properties;

    Nickel

    ?2016 Chinese Society of Aeronautics and Astronautics.Production and hosting by Elsevier Ltd.Thisisan open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).

    *Corresponding author.

    E-mail addresses:renjianrun@163.com(J.Ren),zhuzw@nuaa.edu.cn(Z.Zhu),dzhu@nuaa.edu.cn(D.Zhu).

    Peer review under responsibility of Editorial Committee of CJA.

    Production and hosting by Elsevier

    http://dx.doi.org/10.1016/j.cja.2016.05.001

    1000-9361?2016 Chinese Society of Aeronautics and Astronautics.Production and hosting by Elsevier Ltd.

    This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).

    国产xxxxx性猛交| 99精品久久久久人妻精品| 超碰成人久久| 国产成人精品在线电影| 精品第一国产精品| 国产不卡一卡二| 久久久久视频综合| 精品亚洲成国产av| 99久久精品国产亚洲精品| 欧美日韩黄片免| 后天国语完整版免费观看| 少妇 在线观看| 亚洲av日韩在线播放| 91九色精品人成在线观看| 国产男女超爽视频在线观看| 美女福利国产在线| 成人免费观看视频高清| 王馨瑶露胸无遮挡在线观看| 岛国毛片在线播放| 一区二区三区国产精品乱码| 视频区欧美日本亚洲| 大片免费播放器 马上看| 国产一区二区三区在线臀色熟女 | 少妇裸体淫交视频免费看高清 | 国产一区二区三区综合在线观看| 高潮久久久久久久久久久不卡| 人人妻人人爽人人添夜夜欢视频| 国产成人av激情在线播放| 亚洲精品粉嫩美女一区| 亚洲成人手机| 久久中文字幕一级| 超碰成人久久| 母亲3免费完整高清在线观看| 欧美精品亚洲一区二区| 免费看十八禁软件| 久久久精品区二区三区| 成人黄色视频免费在线看| 在线观看免费午夜福利视频| 久久精品成人免费网站| 久久久水蜜桃国产精品网| 涩涩av久久男人的天堂| 老汉色av国产亚洲站长工具| 黄片播放在线免费| 视频区欧美日本亚洲| av不卡在线播放| 一级,二级,三级黄色视频| 美女视频免费永久观看网站| 精品国内亚洲2022精品成人 | 亚洲成人手机| 亚洲精品中文字幕一二三四区 | 国产午夜精品久久久久久| 考比视频在线观看| 妹子高潮喷水视频| 久久精品国产综合久久久| 亚洲免费av在线视频| 久久久久久久精品吃奶| 国产精品久久久人人做人人爽| 人人澡人人妻人| 99国产综合亚洲精品| 亚洲欧美精品综合一区二区三区| 91国产中文字幕| 自线自在国产av| 成年女人毛片免费观看观看9 | 国产片内射在线| 亚洲成av片中文字幕在线观看| 一区二区三区国产精品乱码| 99国产精品一区二区蜜桃av | 丁香六月欧美| 99国产精品一区二区蜜桃av | 高潮久久久久久久久久久不卡| 精品久久久久久久毛片微露脸| 色婷婷久久久亚洲欧美| 久久天躁狠狠躁夜夜2o2o| 美女视频免费永久观看网站| 女人精品久久久久毛片| 国产av一区二区精品久久| 天堂8中文在线网| 一夜夜www| 欧美成人午夜精品| 黄色片一级片一级黄色片| 久久精品熟女亚洲av麻豆精品| 久久99热这里只频精品6学生| 狠狠婷婷综合久久久久久88av| 一级黄色大片毛片| 视频在线观看一区二区三区| 亚洲av成人不卡在线观看播放网| 高清在线国产一区| 天天添夜夜摸| 亚洲中文字幕日韩| 国产精品秋霞免费鲁丝片| 午夜福利乱码中文字幕| 啦啦啦视频在线资源免费观看| 亚洲国产精品一区二区三区在线| 999精品在线视频| 老司机福利观看| 日韩三级视频一区二区三区| 热re99久久国产66热| 免费看十八禁软件| 女人高潮潮喷娇喘18禁视频| 青青草视频在线视频观看| 国产精品av久久久久免费| 国产精品久久久久久精品电影小说| 嫁个100分男人电影在线观看| 婷婷成人精品国产| 性高湖久久久久久久久免费观看| 欧美乱码精品一区二区三区| 亚洲黑人精品在线| 亚洲精品中文字幕在线视频| 亚洲伊人久久精品综合| 国产精品免费视频内射| 麻豆国产av国片精品| 国产野战对白在线观看| 国产片内射在线| 露出奶头的视频| 两性午夜刺激爽爽歪歪视频在线观看 | h视频一区二区三区| 啦啦啦中文免费视频观看日本| 国产亚洲精品久久久久5区| 一级a爱视频在线免费观看| 国产av又大| 老司机午夜福利在线观看视频 | 国产又色又爽无遮挡免费看| 日韩大片免费观看网站| 自线自在国产av| 午夜激情久久久久久久| 老汉色av国产亚洲站长工具| 搡老熟女国产l中国老女人| 国产成人影院久久av| 伊人久久大香线蕉亚洲五| 熟女少妇亚洲综合色aaa.| 男女床上黄色一级片免费看| 在线观看舔阴道视频| 午夜福利在线观看吧| 国产成人欧美| 国产精品美女特级片免费视频播放器 | 欧美激情 高清一区二区三区| 午夜91福利影院| 大香蕉久久成人网| 国产亚洲精品第一综合不卡| 欧美精品av麻豆av| 日韩视频一区二区在线观看| 国产精品免费视频内射| 亚洲国产av影院在线观看| 人妻 亚洲 视频| 丁香六月欧美| 夜夜夜夜夜久久久久| 日韩欧美一区二区三区在线观看 | 国产精品免费一区二区三区在线 | 深夜精品福利| 成年人午夜在线观看视频| 日韩一卡2卡3卡4卡2021年| 国产一卡二卡三卡精品| 我要看黄色一级片免费的| 欧美精品一区二区免费开放| 免费少妇av软件| 99国产精品99久久久久| 又大又爽又粗| 欧美av亚洲av综合av国产av| 看免费av毛片| 午夜福利在线观看吧| 国产精品久久久久久精品古装| 成人国语在线视频| 女人久久www免费人成看片| 变态另类成人亚洲欧美熟女 | 我要看黄色一级片免费的| 午夜精品久久久久久毛片777| avwww免费| 咕卡用的链子| 999久久久精品免费观看国产| 欧美另类亚洲清纯唯美| 天天添夜夜摸| 飞空精品影院首页| 熟女少妇亚洲综合色aaa.| 久久精品人人爽人人爽视色| 国产无遮挡羞羞视频在线观看| 亚洲avbb在线观看| 国产一区二区三区在线臀色熟女 | 精品少妇一区二区三区视频日本电影| 色婷婷av一区二区三区视频| 日本精品一区二区三区蜜桃| 老熟妇乱子伦视频在线观看| 欧美一级毛片孕妇| 久久中文字幕一级| 99国产极品粉嫩在线观看| 国产av国产精品国产| 精品熟女少妇八av免费久了| 高清av免费在线| 国产成人一区二区三区免费视频网站| 高清毛片免费观看视频网站 | 亚洲五月色婷婷综合| 成年女人毛片免费观看观看9 | 国产aⅴ精品一区二区三区波| 高清黄色对白视频在线免费看| 亚洲国产毛片av蜜桃av| 国产亚洲精品一区二区www | 久久精品aⅴ一区二区三区四区| 咕卡用的链子| 国产精品99久久99久久久不卡| 9热在线视频观看99| 国产亚洲精品一区二区www | 色精品久久人妻99蜜桃| 日韩欧美免费精品| 日韩成人在线观看一区二区三区| 成人永久免费在线观看视频 | 女人爽到高潮嗷嗷叫在线视频| 成人特级黄色片久久久久久久 | 99久久精品国产亚洲精品| 亚洲av日韩精品久久久久久密| 天天躁夜夜躁狠狠躁躁| 在线观看免费高清a一片| 操出白浆在线播放| 亚洲精品中文字幕在线视频| 精品国产乱子伦一区二区三区| 中文欧美无线码| 久久天堂一区二区三区四区| 欧美成人午夜精品| 青青草视频在线视频观看| 中文欧美无线码| 成年人免费黄色播放视频| 国产欧美日韩一区二区三区在线| 亚洲精品av麻豆狂野| 在线观看免费午夜福利视频| 大香蕉久久网| 黑人巨大精品欧美一区二区蜜桃| 最新美女视频免费是黄的| 电影成人av| 国产又爽黄色视频| 午夜福利影视在线免费观看| 最新在线观看一区二区三区| 免费女性裸体啪啪无遮挡网站| 在线观看一区二区三区激情| 久久精品亚洲熟妇少妇任你| av又黄又爽大尺度在线免费看| 欧美精品一区二区大全| 亚洲精品久久成人aⅴ小说| 老司机在亚洲福利影院| 在线播放国产精品三级| 亚洲成人国产一区在线观看| 丰满少妇做爰视频| 日韩有码中文字幕| 老司机影院毛片| 蜜桃国产av成人99| 亚洲成人手机| 久久久久国产一级毛片高清牌| 夜夜爽天天搞| 久久av网站| 午夜激情av网站| 国产男女内射视频| 一边摸一边抽搐一进一小说 | 国产片内射在线| 亚洲色图 男人天堂 中文字幕| 另类亚洲欧美激情| 精品福利观看| 91大片在线观看| 国产精品久久久久久人妻精品电影 | 91精品国产国语对白视频| 性少妇av在线| 亚洲精品中文字幕一二三四区 | 十八禁人妻一区二区| 久久精品国产亚洲av香蕉五月 | 国产成人欧美在线观看 | 亚洲色图av天堂| 2018国产大陆天天弄谢| a在线观看视频网站| 国产亚洲欧美在线一区二区| 极品少妇高潮喷水抽搐| 九色亚洲精品在线播放| 人人妻人人添人人爽欧美一区卜| 精品久久久久久电影网| 精品福利永久在线观看| 精品人妻熟女毛片av久久网站| 99久久人妻综合| 国产精品一区二区精品视频观看| 久久青草综合色| 欧美日韩福利视频一区二区| 日本a在线网址| 十八禁网站网址无遮挡| 欧美精品高潮呻吟av久久| 国产精品一区二区精品视频观看| 精品国内亚洲2022精品成人 | 高清av免费在线| 美女主播在线视频| 大型av网站在线播放| 日韩三级视频一区二区三区| 国产一区有黄有色的免费视频| 免费在线观看完整版高清| 久久人妻熟女aⅴ| 黑人欧美特级aaaaaa片| 亚洲色图综合在线观看| 精品卡一卡二卡四卡免费| 两性午夜刺激爽爽歪歪视频在线观看 | a级毛片在线看网站| 欧美日韩中文字幕国产精品一区二区三区 | 最新的欧美精品一区二区| 精品久久久久久久毛片微露脸| 日韩欧美一区二区三区在线观看 | 欧美激情高清一区二区三区| 一夜夜www| 母亲3免费完整高清在线观看| 成人手机av| 女人精品久久久久毛片| 久9热在线精品视频| 黄频高清免费视频| 亚洲精品国产精品久久久不卡| 热99久久久久精品小说推荐| 国产一区二区三区视频了| 老司机亚洲免费影院| 在线观看免费高清a一片| 国产人伦9x9x在线观看| 可以免费在线观看a视频的电影网站| 国产精品成人在线| 精品福利永久在线观看| 成人亚洲精品一区在线观看| 两个人免费观看高清视频| 自线自在国产av| 999久久久精品免费观看国产| 久久久精品区二区三区| 精品国产超薄肉色丝袜足j| 动漫黄色视频在线观看| 精品国产亚洲在线| 久久久久久免费高清国产稀缺| 在线观看www视频免费| 老汉色∧v一级毛片| 老司机靠b影院| 日韩免费av在线播放| 久久人人97超碰香蕉20202| 亚洲色图av天堂| 色视频在线一区二区三区| 国产精品免费大片| 久久午夜亚洲精品久久| 久久精品91无色码中文字幕| 国内毛片毛片毛片毛片毛片| 精品少妇黑人巨大在线播放| 亚洲欧美色中文字幕在线| 成人国产一区最新在线观看| 国产无遮挡羞羞视频在线观看| 亚洲欧美精品综合一区二区三区| 亚洲中文日韩欧美视频| 怎么达到女性高潮| 精品第一国产精品| 国产人伦9x9x在线观看| 午夜激情久久久久久久| 亚洲精品乱久久久久久| 99热网站在线观看| 一区二区av电影网| 一进一出抽搐动态| 69精品国产乱码久久久| 国产色视频综合| 成年人黄色毛片网站| 视频在线观看一区二区三区| 精品福利永久在线观看| 亚洲七黄色美女视频| 免费女性裸体啪啪无遮挡网站| 国产男女超爽视频在线观看| 久久久精品免费免费高清| 亚洲国产看品久久| 精品国产一区二区三区四区第35| tube8黄色片| 国产日韩欧美亚洲二区| 十八禁高潮呻吟视频| 老司机靠b影院| 丝袜在线中文字幕| 日韩中文字幕欧美一区二区| 黄网站色视频无遮挡免费观看| 国产亚洲av高清不卡| 日韩一区二区三区影片| 麻豆乱淫一区二区| 在线观看免费视频日本深夜| 精品少妇一区二区三区视频日本电影| 亚洲专区国产一区二区| 又紧又爽又黄一区二区| 国产日韩欧美视频二区| 中文亚洲av片在线观看爽 | 一区二区三区激情视频| 国产日韩欧美视频二区| 建设人人有责人人尽责人人享有的| 一级a爱视频在线免费观看| 亚洲精品成人av观看孕妇| 国产日韩欧美视频二区| 夜夜骑夜夜射夜夜干| 亚洲自偷自拍图片 自拍| 在线观看舔阴道视频| 亚洲中文日韩欧美视频| 窝窝影院91人妻| 国产1区2区3区精品| 亚洲成人手机| 国产精品一区二区免费欧美| 久久青草综合色| 男男h啪啪无遮挡| 99久久99久久久精品蜜桃| 丰满少妇做爰视频| 我要看黄色一级片免费的| 五月天丁香电影| 变态另类成人亚洲欧美熟女 | 热99久久久久精品小说推荐| 热99久久久久精品小说推荐| 国产主播在线观看一区二区| 日韩 欧美 亚洲 中文字幕| 国产免费av片在线观看野外av| 久久久欧美国产精品| 免费高清在线观看日韩| 黄频高清免费视频| 亚洲五月婷婷丁香| 一本大道久久a久久精品| 日韩三级视频一区二区三区| 日本一区二区免费在线视频| 午夜日韩欧美国产| 欧美av亚洲av综合av国产av| 男女之事视频高清在线观看| 亚洲综合色网址| 在线观看66精品国产| 日韩视频在线欧美| 国产一区二区三区在线臀色熟女 | 黄色a级毛片大全视频| 免费日韩欧美在线观看| www.自偷自拍.com| 亚洲男人天堂网一区| 人成视频在线观看免费观看| 精品一区二区三区四区五区乱码| 久久国产精品人妻蜜桃| 欧美国产精品va在线观看不卡| 999精品在线视频| 国产免费av片在线观看野外av| 亚洲人成电影免费在线| 91精品国产国语对白视频| 久久av网站| 国产高清国产精品国产三级| 国产精品香港三级国产av潘金莲| 久久精品国产99精品国产亚洲性色 | 日日摸夜夜添夜夜添小说| 国产高清激情床上av| 色婷婷av一区二区三区视频| 久久久久久久大尺度免费视频| 国产成人影院久久av| 成年版毛片免费区| 久久久水蜜桃国产精品网| 国产高清国产精品国产三级| 免费少妇av软件| 亚洲伊人久久精品综合| 91字幕亚洲| 中文字幕人妻熟女乱码| 女人被躁到高潮嗷嗷叫费观| 制服诱惑二区| 欧美日韩黄片免| 桃红色精品国产亚洲av| 亚洲专区国产一区二区| 男女下面插进去视频免费观看| 99久久99久久久精品蜜桃| 啦啦啦 在线观看视频| 久久人妻av系列| h视频一区二区三区| 最新在线观看一区二区三区| 久久久久久久国产电影| 嫁个100分男人电影在线观看| 9热在线视频观看99| 欧美在线一区亚洲| 精品国内亚洲2022精品成人 | 国产野战对白在线观看| 国产精品秋霞免费鲁丝片| 老熟女久久久| 男女下面插进去视频免费观看| 精品高清国产在线一区| videosex国产| 国产一区二区 视频在线| 一进一出好大好爽视频| av一本久久久久| 1024香蕉在线观看| 欧美大码av| 欧美黑人精品巨大| 人妻久久中文字幕网| 日本五十路高清| 99热网站在线观看| 精品亚洲乱码少妇综合久久| 性少妇av在线| 男女午夜视频在线观看| 老司机午夜十八禁免费视频| av线在线观看网站| 女警被强在线播放| 天天躁夜夜躁狠狠躁躁| 最黄视频免费看| 飞空精品影院首页| 后天国语完整版免费观看| 动漫黄色视频在线观看| 一边摸一边抽搐一进一小说 | 精品国产超薄肉色丝袜足j| 1024视频免费在线观看| av免费在线观看网站| 欧美激情极品国产一区二区三区| 成人影院久久| 国产不卡av网站在线观看| 国产成人啪精品午夜网站| 亚洲美女黄片视频| 首页视频小说图片口味搜索| 在线观看一区二区三区激情| 欧美另类亚洲清纯唯美| 国产精品久久久av美女十八| 人妻久久中文字幕网| 国产淫语在线视频| 男女高潮啪啪啪动态图| h视频一区二区三区| 色尼玛亚洲综合影院| 他把我摸到了高潮在线观看 | 日韩精品免费视频一区二区三区| 国产成人啪精品午夜网站| 欧美黑人精品巨大| 久久久久精品国产欧美久久久| 国产又爽黄色视频| 日本vs欧美在线观看视频| 男人舔女人的私密视频| 欧美日韩福利视频一区二区| 亚洲精品在线美女| 在线观看免费日韩欧美大片| 亚洲欧美激情在线| 久久精品91无色码中文字幕| 黄色成人免费大全| 一级,二级,三级黄色视频| 亚洲精品一卡2卡三卡4卡5卡| 国产成人精品无人区| 一边摸一边抽搐一进一出视频| 交换朋友夫妻互换小说| 亚洲一区中文字幕在线| 国产成人精品久久二区二区91| 亚洲一区中文字幕在线| 交换朋友夫妻互换小说| 97人妻天天添夜夜摸| 1024视频免费在线观看| 麻豆乱淫一区二区| 大香蕉久久成人网| 丝袜在线中文字幕| 免费在线观看黄色视频的| 狠狠精品人妻久久久久久综合| 女警被强在线播放| 亚洲成人免费av在线播放| 丰满迷人的少妇在线观看| 99国产综合亚洲精品| 黄网站色视频无遮挡免费观看| 国产成人免费观看mmmm| 亚洲av美国av| 欧美性长视频在线观看| 久久香蕉激情| 国产又色又爽无遮挡免费看| 久久 成人 亚洲| cao死你这个sao货| 久久久久久久大尺度免费视频| 精品欧美一区二区三区在线| 啦啦啦 在线观看视频| 老司机深夜福利视频在线观看| 制服诱惑二区| 国产又色又爽无遮挡免费看| 国产1区2区3区精品| 亚洲av欧美aⅴ国产| 伊人久久大香线蕉亚洲五| 高清在线国产一区| 俄罗斯特黄特色一大片| 天堂俺去俺来也www色官网| 女人精品久久久久毛片| 亚洲久久久国产精品| 又黄又粗又硬又大视频| 69精品国产乱码久久久| 午夜福利欧美成人| 国产免费视频播放在线视频| 亚洲精华国产精华精| 老熟女久久久| 人妻久久中文字幕网| 亚洲精品美女久久久久99蜜臀| 色老头精品视频在线观看| 18禁黄网站禁片午夜丰满| 热99久久久久精品小说推荐| 一本综合久久免费| 青草久久国产| 男女无遮挡免费网站观看| 精品高清国产在线一区| 超色免费av| 少妇精品久久久久久久| 高潮久久久久久久久久久不卡| 久久精品国产亚洲av高清一级| 久久久久久久大尺度免费视频| 免费av中文字幕在线| 99国产综合亚洲精品| 欧美日韩黄片免| 亚洲精品国产一区二区精华液| 91成年电影在线观看| 天堂俺去俺来也www色官网| 亚洲国产欧美在线一区| 19禁男女啪啪无遮挡网站| 变态另类成人亚洲欧美熟女 | 另类亚洲欧美激情| 日韩免费高清中文字幕av| 国产熟女午夜一区二区三区| 两个人免费观看高清视频| 一本久久精品| 免费观看a级毛片全部| 久久久精品免费免费高清| 一区二区三区乱码不卡18| 免费观看a级毛片全部| 考比视频在线观看| 夜夜骑夜夜射夜夜干| 精品熟女少妇八av免费久了| kizo精华| 国产老妇伦熟女老妇高清| 精品一区二区三区四区五区乱码| 午夜福利,免费看| 激情在线观看视频在线高清 | 夜夜骑夜夜射夜夜干| 欧美日韩福利视频一区二区| 久久天堂一区二区三区四区| 久久精品亚洲熟妇少妇任你| 一区二区av电影网| 亚洲成av片中文字幕在线观看| 欧美精品亚洲一区二区| 日韩大片免费观看网站| 日韩三级视频一区二区三区| 在线观看免费视频日本深夜| 精品午夜福利视频在线观看一区 | 搡老乐熟女国产|