• <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 ?

    Theoretical and numerical investigations on the headspace of cartridge cases considering axial deformation and movement

    2020-04-09 18:37:40SongCaiChenleiHuangKunLiuZhongxinLiZhilinWu
    Defence Technology 2020年1期

    Song Cai,Chen-lei Huang,Kun Liu,Zhong-xin Li,Zhi-lin Wu

    School of Mechanical Engineering,Nanjing University of Science and Technology,Nanjing 210094,Jiangsu,China

    Keywords:Cartridge case headspace Radial clearance Thick-walled cylinder Dynamic response

    ABSTRACT The cartridge case headspace is the axial clearance between the cartridge and bolt of an automatic weapon,and influences the reliability and security of the weapon.Accordingly,theoretical and numerical studies were conducted to analyze the dynamic response of cartridge cases during internal impact considering the initial radial clearances between the cartridge case and chamber.A theoretical model was proposed to predict the cartridge case headspace considering both the deformation and movement of the cartridge case and confirmed by the results of nonlinear finite element simulations.The differences between the results of the conventional static model and the dynamic model were then comprehensively evaluated.The effects of the angle between the cartridge and chamber,the cartridge case material,and the internal impact pressure on the predicted headspace value were also analyzed.The dynamic response of the cartridge case predicted by the dynamic model was more accurate than that predicted by the conventional static model.The internal impact pressure,pressure change rate,and cartridge material were all found to affect the predicted headspace.?2020 China Ordnance Society.Production and hosting by Elsevier B.V.on behalf of KeAi Communications Co.This is an open access article under the CCBY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).

    1.Introduction

    Clearances in machines are unavoidable due to manufacturing tolerances,assemblage,wear,and material deformation.In order to better describe the influence of clearances,many clearance analysis models[1-3]have been constructed.Meanwhile,the influence of clearance has been widely studied in various fields such as mechanical engineering[4-10],manufacturing[11],aerospace[12-15],and robotics[16-18].How ever,these studies only concern radial clearances,while axial clearances have been scarcely considered.Headspace is the axial clearance between the cartridge and the breech bolt,or between the bolt and the receiver.Inappropriate headspace may lead to failure to fire or rupture,possibly damaging the firearm and injuring the shooter[19].The headspace is also an important service life criterion of automatic weapons[20].

    Over the last few decades,a significant number of researchers have studied the clearance effects on the dynamic response of weapons under blast loading.Xie and Yang[21]studied the influence of clearances on shooting accuracy,considering the radial clearance between trunnions and bearings.In Tasson and Sadowski[22],the axial clearance had a more significant influence on the maximum stress during internal impact than the radial clearance.Xu[23]and Dong[24]demonstrated the influence of headspace on the firearm bolt.Therefore,prediction of the maximum effective headspace of an automatic weapon is a significant consideration in engineering.Gordon[25]constructed a model to calculate the force and deformation of a cartridge in a chamber.Xuebing[19]and Wang[26]constructed a static analytical model that regards the axial deformation of a cartridge under the quasi-static condition as the maximum headspace.Shao-Min[27]and Cai[28]analyzed the maximum headspace of 12.7 mm cartridge cases with numerical simulations.These numerical analyses all indicated that the maximum headspace was greater than the cartridge deformation during f i ring.

    Based on such previous research,this study attempts to predict the maximum headspace of cartridge cases using a theoretical approach.First,the deformation and movement of the cartridge during firing was calculated.A theoretical dynamic model was then constructed to characterize the maximum headspace of a gun and its results were confirmed by numerical simulations.The differences between the static model and the dynamic model under different material parameters,internal blast pressures,and structural parameters were then explored.

    2.Theoretical dynamic model of head space

    2.1.Fundamental assumptions

    The deformation and movement of a cartridge in a gun chamber under the influence of propellant gas is quite complex.Due to the initial radial clearance between the cartridge and chamber,the contact state varies with the pressure inside the chamber.When t=0,the neck of the cartridge is just in contact with the chamber;at this time,the axial pressure on the cartridge is greater than the frictional resistance between the cartridge and the chamber,allowing the cartridge to move axially.As the pressure increases,the radial clearance is eliminated,leading to an increase in the contact area and pressure between the cartridge and the chamber,accordingly increasing the frictional resistance.Once this frictional resistance is greater than the axial pressure,the cartridge tends to behave statically,and after the cartridge has stopped moving,the resulting axial force causes the cartridge to axially deform.The axial deformation and displacement of the cartridge therefore both act to eliminate the headspace,resulting in complex dynamic cartridge behavior during the ballistic cycle.For ease of application and discussion of the equations,the following assumptions have been made in this study:

    1)The cartridge is an axisymmetric,thick-walled cylinder,the shoulder and neck are neglected,and the chamber is an inner conical tube.

    2)The deformation of the cartridge is considered during the rising pressure stage and the pressure is linearly related to time.

    3)The cartridge and chamber are isotropic materials and their deformations remain within the elastic deformation range.

    4)The influence of temperature is neglected.

    2.2.Cartridge and chamber model

    The model used for the calculations is shown in Fig.1,in which the inner diameter of the cartridge is 2a and its outer diameter is 2b;the outer diameter of the chamber is 2c;the angle between chamber and cartridge is β;the depth of the cartridge is l;the inside pressure of the cartridge is p;the elastic modulus and Poisson's ratio of the chamber are E1and ν1,respectively;the elastic modulus and Poisson's ratio of the cartridge are E2and ν2,respectively;the cartridge and chamber are isotropic materials;the sliding coefficient of friction between the cartridge and chamber is μ;and the maximum static coefficient of friction is identical to the sliding coefficient of friction.

    2.2.1.Contact pressure between the cartridge and chamber

    Once the cartridge is inserted into the chamber,there is an initial radial clearance δ between the two as follows:

    As the ballistic cycle begins,the cartridge case expands to make contact with the inside of the chamber under pressure,after which the two simultaneously deform.Assuming that the cartridge and chamber are both thick-walled cylinders,according to Lame's equations[29]the following equation can be obtained to describe the displacement:

    When the pressure inside the cartridge is p and the contact pressure between the cartridge and the chamber is pj,according to Eq.(1),the displacement of the outside wall of the cartridge ukand displacement of the inner wall of the chamber utcan be obtained as:

    When the cartridge contacts the chamber,the deformation between the chamber and cartridge follow s the compatibility equation:

    Fig.1.Cartridge and chamber model.

    Combining Eq.(1)-Eq.(5),the contact pressure between the cartridge and chamber pjcan be obtained as follows:

    When pj=0,according to Eq.(6),the real contact length lcbetween the cartridge and chamber can be obtained as:

    When lc=l,according to Eq.(6),the pressure at this time,pl,is given by:

    Therefore,the inside pressure p≥pl,so the cartridge is in complete contact with the chamber.

    2.2.2.Axial elongation of cartridge

    In a conventional model,the cartridge case experiences a static deformation under pressure.How ever,the contact length lcis not fixed equal to the depth of the cartridge,but rather varies as the pressure changes.The dynamic model must therefore calculate the axial deformation of the cartridge using the forces shown in Fig.2.In this model,the friction force on the cartridge case is not uniformly distributed,but rather consists of a static friction region located in the range[0,ls],where lsis the static friction length,and a sliding friction region located in the range[ls,lc].

    The friction force on the microelement shown in Fig.2 is given by:

    where Sc=2πb is the surface coefficient and μ is the sliding friction coefficient.

    The strain on the microelement caused by the friction force is:

    where Sj=π(b2-a2)is the cross-sectional area of the cartridge.

    Fig.2.Force and stress on a cartridge microelement.

    The axial elongation caused by the friction force is:

    The friction on point y=lcfollows the function flc=p S,where S=πa2.Substituting Eq.(6)into Eq.(9),the friction on the cartridge case can be expressed as:

    When β=0,only sliding region[ls,lc],expressed as the limiting length in the Automatic Weapons and Ammunition Infantry Design Handbook[20],will be influenced by sliding friction force and the static friction force flsis zero.Therefore,substituting fls=0 and tan β=0 into Eq.(12),the static friction length can be obtained as:

    Combining Eq.(10),Eq.(11),Eq.(12),and Eq.(13),the axial elongation at point y=lccan be determined as:

    where Δlsis the axial elongation at point y=ls.

    When β=0 and fls=0,the forces in the static region[0,ls]can be simplified as a plane strain problem in elastic theory.According to Lame's Eq.(29),the axial strain caused by circumferential and radial deformation can be obtained by:

    Substituting Eq.(15)into Eq.(11),the axial elongation of static region[0,ls]is determined as:

    When β≠0,the friction is evenly distributed along the surface of static region[0,ls],andUsing Eq.(10)and Eq.(11),the strain and elongation at point y=lscan be written as:

    Combining Eq.(12)and Eq.(13),the friction at point y=lscan be obtained by:

    Combining Eq.(13),Eq.(18),and Eq.(19),the total axial deflection of the static region[0,ls]is:

    Combining Eq.(14),Eq.(16),and Eq.(20),the axial deflection of the cartridge can be obtained as:

    If pd>pmax,where pmaxis the maximum pressure on the inner cartridge case,the cartridge will continue to move,while if,the cartridge will stop moving.Becausev d t and,using Eq.(24)the equation for axial movement can be obtained as:

    2.2.3.Axial movement of cartridge

    When moving axially,according to Eq.(6)and Eq.(9),the sliding friction on the cartridge is given by:

    With increasing pressure,the contact length between the cartridge and chamber increases.When the pressure is fairly low,the cartridge and chamber are not in complete contact with each other,that is,p≤l and the contact length is lc.Substituting Eq.(7)into Eq.(22),the friction can be obtained as:

    Assuming that the inside pressure p=kt,where k is the rate of pressure increase and t is the time of movement,given an initial speed v|t=0=0,the axial speed of the cartridge is:

    where M is the mass of all moving parts.

    In order for the cartridge to stop moving,conditions must match p S<f.Once complete contact has occurred,the contact length of the cartridge does not increase again,but the cartridge is still moving,and the cartridge must continue to move.Therefore,the stationary condition of the cartridge is p≤pl,and given v=0 in Eq.(24),the stop conditions,expressed as the time tdand pressure pdof the cartridge,can be obtained as follows:

    Substituting tdin Eq.(25)into Eq.(27)provides the total axial displacement of the cartridge:

    This axial motion is described by an increment of the contact pressure Δpj=-CδΔmtan β,an increment of the friction Δf=-and an average increment of the accelerationtan β.Substituting these expressions into Eq.(27)provides the equation for the increment of axial motion as follow s:

    and the axial displacement of the cartridge Δdcan then be modified to:

    Fig.3.Finite element model of the cartridge and chamber.

    Table 1 Parameters of structure and materials of numerical simulation.

    2.2.4.Dynamic headspace

    In the dynamic headspace model,the axial clearance is eliminated through axial motion Δmand axial deformation Δs,so the maximum dynamic headspace is given by:

    where Δsand Δmare calculated according to Eq.(21)and Eq.(30),respectively.

    3.Numerical simulation

    Both the deformation and motion of the cartridge occur within an extremely short period of time during f i ring.Furthermore,throughout the entire course of firing,the cartridge is located inside the chamber,making it difficult to observe and record its deformation and motion.Therefore,to verify the proposed theoretical model,a cartridge-chamber finite element model(FEM)based on a 12.7-mm machine gun,shown in Fig.3,was constructed in the ANSYS FEM software package using the parameters shown in Table 1.

    The axisymmetric element“plane 183”was adopted to build the FEM,and the axial displacement of the chamber was constrained.The contact between the cartridge and the chamber was calculated using the penalty function method,the maximum pressure was 300 MPa,a transient analysis was conducted using a ramped-load method,and the calculation time was 0.75 ms.

    4.Results and discussion

    4.1.Error analysis between theoretical model and FEM

    Using the parameters in Table 1,Eq.(31)was calculated using MATLAB,while the deformation and motion of the cartridge was modelled using the FEM.Taking the Y-direction displacement of the cartridge head as the maximum headspace in the dynamic model(Δd),and the Y-direction displacement of cartridge mouth as the axial movement(Δm),the subtraction ofΔmfrom Δdprovides the maximum headspace of the static model(Δs)of the cartridge,with the results shown in Table 2.

    It is clear from the table that there is only a small difference between the FEM results and the theoretical values,amounting to less than 10%,indicating good agreement.When β=0 in Eq.(28),indicating that the initial radial clearance is zero,→0,thus Eq.(9)and Eq.(10)can be simplified into),which formally agrees with the expressionin conventional static theory[20],suggesting that the conventional static theory is a simplified model of the dynamic theory.The maximum headspace determined by the conventional static model is far smaller than that determined using the dynamic model,and with the increase in angle β,this difference gradually increases,indicating that axial motion is an important portion of the dynamic behavior of the cartridge in the chamber,and thus should not be ignored.

    4.2.Parameter effects

    Material parameters and pressure conditions have a remarkable influence on the design of lightweight cartridge cases[22].A onefactor analysis was used to study the effects of the different basic parameters defined for use in the experiments and shown in Table 1.The influence of these pressure and cartridge case material parameters on the dynamic model headspace(Δd),static model headspace due to only axial deformation(Δs),and dynamic axial motion(Δm)was evaluated by calculating the headspace while changing the single parameter in question.

    Fig.4.Influence of maximum pressure on headspace,in which the maximum pressure P max is changed while the other parameters are held constant at their values shown in Table 1.

    Table 2 Errors between the results of theoretical model and FEM.

    4.2.1.Influence of pressure

    The headspace calculated using the dynamic model(Δdand FEM_Δd),as represented by Eq.(31),was always greater than that calculated using the static model(Δsand FEM_Δs),as shown in Fig.4 and Fig.5.As can be seen in Fig.4,with the increase in pressure,the dynamic solution gradually decreases because the dynamic axial motion(Δmand FEM_Δm),calculated by Eq.(30),tends to zero.When the pressure is low,the axial deformation of the cartridge is low,as is the friction,meaning that axial motion is the main component affecting the reduction of headspace.

    In Fig.4,as the pressure increases from 150 MPa to 500 MPa,the headspace due to the axial deformation of the cartridge(Δsand FEM_Δs)increases gradually.From Eq.(21),note that a large axial deformation of cartridge increases the risk of transverse rupture of the cartridge.

    As shown in Fig.5,keeping d p/d t=k constant,the movement of the cartridge is also constant.It can therefore be concluded that the movement of the cartridge(Δmand FEM_Δm)is related to the rate of pressure increase d p/d t.The expression Δm∝1/k2can be obtained from Eq.(28),indicating that as d p/d t increases,the dynamic axial movement of the cartridge(Δm)decreases.With the continued increase in pressure up to Pmax,d p/d t decreases,and thus the dynamic axial movement(Δm)of the cartridge also decreases in accordance with Eq.(28),as shown in Fig.5.

    Fig.6 indicates that when the maximum pressure remains constant and as the time of maximum pressure(tmax)increases,the maximum dynamic headspace(Δdand FEM_Δd)of the cartridge increases with time.Though the static deformation of the cartridge Δsis small,the dynamic axial movement Δmof the cartridge is obvious.After 0.7 ms,the dynamic axial movement Δmof the cartridge is obviously greater than the static axial deformation Δsof the cartridge.

    The increase in cartridge case static axial deformation(Δs)leads to an increase in the risk of cartridge rupture[20].In order to increase the ability of the cartridge to adapt to the chamber,the dynamic axial movement Δmshould be increased and Δsshould be decreased.Therefore,a decrease in pressure and an increase in its application rate should be adopted to enhance the safety of the cartridge in the chamber.

    Fig.5.Influence of maximum pressure on headspace,determined by keeping d p/d t=k constant so that the maximum pressure P max changes with the time of maximum pressure t max.

    Fig.6.Influence of time of maximum pressure t max on headspace with other conditions held constant.

    4.2.2.Influence of material properties

    Currently,brass is widely accepted as the main material used to manufacture gun cartridges due to its excellent performance.How ever,with the continued development of military equipment,requirements for lightweight cartridges have been increasing[22].Different materials have very large differences in their elastic moduli,Poisson's ratios,and densities(Table 3).In this study,a magnesium(Mg)alloy cartridge with a mass of 15.6 g and an aluminum(Al)alloy cartridge with a mass of 24.3 g were selected for comparison with a brass cartridge with a mass of 73.7 g.The feasibility of these two materials in cartridge applications were accordingly evaluated against the performance of brass.

    Due to the motion of the bolt,the headspace can be in any location between moving parts.When axial clearance is present between the cartridge and the bolt,the mass of the cartridge itself is considered,as shown in Fig.7.The maximum headspace(Δd)of the Al alloy cartridge corresponds to that of the brass cartridge,while the maximum headspace(Δd)of the Mg alloy cartridge is only a third that of the brass cartridge.Therefore,both the Al alloy and brass cartridges can guarantee safe use with maximum headspace.

    It was assumed that the headspace was located between bolt and the cartridge case,but when evaluating the motion of the bolt,there may also be gaps between the bolt and the receiver.When headspace exists between the bolt and the receiver,the bolt will slide together with the cartridge case,thus the influence of the mass of the automatic bolt mechanism and its accessories on the model behavior must be considered.In this study,this mass was assumed to be 100 g.As shown in Fig.8,the maximum headspace(Δd)of the Al alloy cartridge is greater than that of the Mg alloy,butboth are approximately half that of the brass cartridge.No matter the location of the gap,the static axial deformation(Δs)of the Mg alloy is always larger than that of the other two materials.Because of the reduced headspace,the adaptability of the Al alloy cartridge and the Mg alloy cartridge to the surrounding environment is clearly inferior to that of the brass cartridge.

    Table 3 Properties of different cartridge materials.

    Fig.7.Influence of material on the movement and deformation of the cartridge in the chamber when the axial clearance is located between the cartridge and the bolt(including the mass of the cartridge).

    Fig.8.Influence of material on the movement and deformation of the cartridge in the chamber when the axial clearance is located between the bolt and receiver(including the mass of the bolt and cartridge).

    As shown in Fig.9,when the mass of the Al alloy,Mg alloy,and brass cartridge/bolt are identical,the axial deformation(Δs)of the Mg cartridge is the largest under the dynamic model,and reaches the failure criterion of the cartridge case[20]at the same clearance as the other materials,indicating that transverse ruptures will tend to occur more readily in a Mg alloy cartridge.For the same mass,the headspace of the Al alloy cartridge is greater than that of the Mg alloy cartridge,but still less than that of the brass cartridge.Clearly,a high elastic modulus helps to increase the maximum headspace of the cartridge.

    Fig.9.Influence of material on cartridge movement and deformation in static and dynamic models for a constant mass of different materials.

    All in all,due to the poor headspace provided and the accompanying poor adaptability,the Mg alloy is not appropriate for use as a cartridge material.Under certain conditions,the environmental adaptability of the Al alloy cartridge corresponds well with that of the brass cartridge,but the comprehensive adaptability of the Al alloy cartridge is smaller than that of the brass cartridge.How ever,if a lightweight cartridge is required,the use of an Al alloy could be considered.

    5.Conclusions

    In this study,the deformation and motion of a cartridge in a gun chamber was theoretically and numerically modelled to determine the headspace under different pressure conditions and cartridge material parameters.The maximum chamber pressure pmax,the rate of pressure increase d p/d t,and the material properties were evaluated as variables,and the movement and deformation of the cartridge in the chamber were both theoretically analyzed and numerically simulated.The results of the theoretical analysis and numerical simulation indicate that:

    (1)The simulation results are in agreement with the results of the theoretical calculation,and the motion of the cartridge along the chamber is revealed to be an important factor in determining headspace,thus should not be neglected in any analytical model.The conventional static theory is determined to be a simplified model of the developed dynamic theory.

    (2)The axial deformation of the cartridge is directly proportional to the maximum chamber pressure pmax,while the axial movement of the cartridge Δdis inversely proportional to the rate of pressure increase d p/d t.Decreasing the chamber pressure and increasing the rate of pressure increase will help to improve the headspace and thus the behavior of the cartridge in the chamber.

    (3)Materials with a high elastic modulus were found to enhance the headspace and thus the environmental adaptability of a cartridge.Specifically,Al alloys were found to be acceptable for use as lightweight alternative materials for cartridge cases.

    The proposed dynamic model can thus provide a helpful theoretical reference when choosing the max cartridge headspace during weapon and bullet design.

    Acknowledgements

    The authors are very grateful for the reviewers' instructive suggestions and careful proofreading.This work was supported by the National Natural Science Foundation of China(Grant Nos.11372137 and 11602025)and Equipment Development Department of the Central Military Commission of China(Grant No.301030905).

    免费在线观看完整版高清| 婷婷色麻豆天堂久久| 国产精品无大码| 中文精品一卡2卡3卡4更新| 两个人看的免费小视频| 国产日韩一区二区三区精品不卡| 日本爱情动作片www.在线观看| 国产 精品1| 免费少妇av软件| 人人妻人人澡人人爽人人夜夜| 欧美亚洲 丝袜 人妻 在线| 国产伦理片在线播放av一区| 婷婷成人精品国产| 亚洲美女视频黄频| 免费播放大片免费观看视频在线观看| 伦理电影大哥的女人| 午夜福利,免费看| 国产精品国产av在线观看| 极品少妇高潮喷水抽搐| 狠狠精品人妻久久久久久综合| 亚洲三区欧美一区| 久热久热在线精品观看| 欧美成人精品欧美一级黄| 日日啪夜夜爽| 青春草视频在线免费观看| 欧美变态另类bdsm刘玥| 欧美激情 高清一区二区三区| 一本一本久久a久久精品综合妖精 国产伦在线观看视频一区 | 极品少妇高潮喷水抽搐| 亚洲成人av在线免费| 99热国产这里只有精品6| 色视频在线一区二区三区| 韩国av在线不卡| 两个人免费观看高清视频| 在线看a的网站| 一本色道久久久久久精品综合| 亚洲婷婷狠狠爱综合网| 少妇精品久久久久久久| 国产有黄有色有爽视频| 亚洲美女视频黄频| 国产免费视频播放在线视频| 97在线人人人人妻| 亚洲成人av在线免费| 成人国产麻豆网| 免费观看性生交大片5| 国产精品一二三区在线看| h视频一区二区三区| 纵有疾风起免费观看全集完整版| 黑人猛操日本美女一级片| 久久久久精品性色| 欧美变态另类bdsm刘玥| 中文天堂在线官网| 青春草亚洲视频在线观看| 亚洲欧美中文字幕日韩二区| 亚洲,欧美精品.| 亚洲av国产av综合av卡| 久久ye,这里只有精品| 午夜激情av网站| 成年女人在线观看亚洲视频| 欧美日韩成人在线一区二区| av国产精品久久久久影院| 香蕉精品网在线| 国产探花极品一区二区| 少妇人妻 视频| 卡戴珊不雅视频在线播放| 久久久久久久国产电影| 久久精品国产亚洲av涩爱| 日本色播在线视频| 精品第一国产精品| 卡戴珊不雅视频在线播放| 一本大道久久a久久精品| 妹子高潮喷水视频| 国产精品一区二区在线观看99| 日韩精品有码人妻一区| 卡戴珊不雅视频在线播放| 丝瓜视频免费看黄片| 90打野战视频偷拍视频| xxx大片免费视频| 国产精品嫩草影院av在线观看| 天天躁狠狠躁夜夜躁狠狠躁| 18禁国产床啪视频网站| 成人免费观看视频高清| 成年女人毛片免费观看观看9 | 国产 一区精品| 青青草视频在线视频观看| 妹子高潮喷水视频| 日韩熟女老妇一区二区性免费视频| 国产精品秋霞免费鲁丝片| 大片免费播放器 马上看| 乱人伦中国视频| 最近中文字幕2019免费版| 桃花免费在线播放| 不卡av一区二区三区| 国产又爽黄色视频| 久久免费观看电影| 美女xxoo啪啪120秒动态图| 国产精品一二三区在线看| 深夜精品福利| 亚洲欧洲国产日韩| 色婷婷久久久亚洲欧美| 人妻 亚洲 视频| 日产精品乱码卡一卡2卡三| 两个人看的免费小视频| 伊人久久国产一区二区| 熟女电影av网| 色哟哟·www| 最近2019中文字幕mv第一页| 91精品三级在线观看| 欧美人与性动交α欧美精品济南到 | 观看美女的网站| 18禁观看日本| 丝袜美腿诱惑在线| 国产日韩一区二区三区精品不卡| 老熟女久久久| 一级片免费观看大全| 丰满乱子伦码专区| 18禁观看日本| 天天操日日干夜夜撸| 国产片内射在线| 欧美亚洲日本最大视频资源| 欧美日韩综合久久久久久| 中国三级夫妇交换| 国产精品免费视频内射| 美女高潮到喷水免费观看| 亚洲伊人久久精品综合| 欧美国产精品va在线观看不卡| 青春草视频在线免费观看| 亚洲精品日韩在线中文字幕| 毛片一级片免费看久久久久| 精品人妻在线不人妻| av在线观看视频网站免费| 人人妻人人添人人爽欧美一区卜| 女人高潮潮喷娇喘18禁视频| 日韩av不卡免费在线播放| 中文字幕最新亚洲高清| 久久 成人 亚洲| 乱人伦中国视频| 狠狠婷婷综合久久久久久88av| 久久久久视频综合| 国产精品国产三级国产专区5o| 黄色配什么色好看| 亚洲综合色网址| 侵犯人妻中文字幕一二三四区| 亚洲精华国产精华液的使用体验| 99热国产这里只有精品6| 日韩欧美精品免费久久| 欧美激情 高清一区二区三区| 免费人妻精品一区二区三区视频| 国产成人精品婷婷| 好男人视频免费观看在线| a级毛片黄视频| 欧美av亚洲av综合av国产av | 午夜免费男女啪啪视频观看| 边亲边吃奶的免费视频| 一区二区av电影网| av天堂久久9| 欧美人与性动交α欧美软件| 麻豆乱淫一区二区| 在线观看免费视频网站a站| 日韩人妻精品一区2区三区| 色视频在线一区二区三区| 国产乱人偷精品视频| 亚洲精品aⅴ在线观看| 久久影院123| 三上悠亚av全集在线观看| 人体艺术视频欧美日本| 欧美精品av麻豆av| 97在线人人人人妻| 91aial.com中文字幕在线观看| 男男h啪啪无遮挡| 国产又爽黄色视频| 成人国产麻豆网| a级毛片黄视频| 99re6热这里在线精品视频| 亚洲美女视频黄频| 建设人人有责人人尽责人人享有的| 国产在线免费精品| 亚洲欧洲精品一区二区精品久久久 | 久久午夜福利片| 欧美97在线视频| 街头女战士在线观看网站| 少妇猛男粗大的猛烈进出视频| 欧美精品高潮呻吟av久久| 视频在线观看一区二区三区| 欧美日韩国产mv在线观看视频| 一区福利在线观看| 国产成人91sexporn| 国产精品免费视频内射| 中文字幕另类日韩欧美亚洲嫩草| 综合色丁香网| 国产淫语在线视频| 少妇人妻久久综合中文| 亚洲三区欧美一区| 成人毛片60女人毛片免费| 久久综合国产亚洲精品| 国产又爽黄色视频| 国产精品秋霞免费鲁丝片| 水蜜桃什么品种好| 你懂的网址亚洲精品在线观看| 伦理电影免费视频| 久久精品国产亚洲av天美| 天天操日日干夜夜撸| 免费观看性生交大片5| 国产成人精品一,二区| 大香蕉久久成人网| 国产在视频线精品| 九草在线视频观看| 国产高清国产精品国产三级| 国产精品蜜桃在线观看| 成人毛片60女人毛片免费| 久久精品久久精品一区二区三区| 青春草视频在线免费观看| 日本午夜av视频| 不卡av一区二区三区| 尾随美女入室| 在线观看三级黄色| 黄色 视频免费看| 精品国产露脸久久av麻豆| 在线观看国产h片| 亚洲国产精品国产精品| 国产精品国产三级专区第一集| 99九九在线精品视频| 国产精品国产av在线观看| 极品人妻少妇av视频| 久久久久精品性色| 99国产综合亚洲精品| 美女xxoo啪啪120秒动态图| 久久精品国产鲁丝片午夜精品| 电影成人av| 免费观看无遮挡的男女| 亚洲欧美成人精品一区二区| 极品人妻少妇av视频| 亚洲五月色婷婷综合| 看十八女毛片水多多多| 精品第一国产精品| 精品国产一区二区三区四区第35| 又大又黄又爽视频免费| 99热全是精品| 国产有黄有色有爽视频| 久久国产亚洲av麻豆专区| 久久婷婷青草| 国产97色在线日韩免费| 妹子高潮喷水视频| 2022亚洲国产成人精品| 色婷婷久久久亚洲欧美| 成人亚洲欧美一区二区av| 搡老乐熟女国产| 精品亚洲乱码少妇综合久久| 亚洲熟女精品中文字幕| 亚洲精品第二区| 大陆偷拍与自拍| 在线观看国产h片| 一个人免费看片子| 亚洲欧美成人综合另类久久久| 亚洲国产色片| 亚洲成人av在线免费| 黄片播放在线免费| 国产色婷婷99| 99热国产这里只有精品6| 水蜜桃什么品种好| 制服丝袜香蕉在线| 丰满少妇做爰视频| 日韩,欧美,国产一区二区三区| 777米奇影视久久| 香蕉精品网在线| 男女边摸边吃奶| 王馨瑶露胸无遮挡在线观看| 91精品三级在线观看| 国产亚洲欧美精品永久| 高清在线视频一区二区三区| 青草久久国产| 狂野欧美激情性bbbbbb| 日本免费在线观看一区| 国产1区2区3区精品| 精品人妻在线不人妻| 亚洲一级一片aⅴ在线观看| 成人二区视频| 婷婷色麻豆天堂久久| 国产免费一区二区三区四区乱码| 亚洲国产日韩一区二区| www.熟女人妻精品国产| 国产一级毛片在线| 高清黄色对白视频在线免费看| 久久影院123| 久久精品久久久久久久性| 国产精品一区二区在线观看99| 丰满迷人的少妇在线观看| 国产xxxxx性猛交| 免费在线观看黄色视频的| 亚洲欧美日韩另类电影网站| 大话2 男鬼变身卡| 国产男女超爽视频在线观看| 久久97久久精品| 日韩在线高清观看一区二区三区| www.熟女人妻精品国产| 80岁老熟妇乱子伦牲交| 国产亚洲午夜精品一区二区久久| 国产又爽黄色视频| 99热网站在线观看| 婷婷色av中文字幕| 国产精品国产三级专区第一集| 成年人午夜在线观看视频| 伦理电影大哥的女人| 国产日韩一区二区三区精品不卡| 80岁老熟妇乱子伦牲交| 多毛熟女@视频| 精品亚洲成国产av| 国产成人91sexporn| 亚洲国产欧美日韩在线播放| 欧美精品一区二区免费开放| 国产老妇伦熟女老妇高清| 成年人免费黄色播放视频| 黑人猛操日本美女一级片| 国产又爽黄色视频| 亚洲成国产人片在线观看| 999久久久国产精品视频| 这个男人来自地球电影免费观看 | 老司机影院成人| 亚洲第一av免费看| 人成视频在线观看免费观看| 亚洲精品国产一区二区精华液| 97人妻天天添夜夜摸| 99re6热这里在线精品视频| av免费观看日本| 午夜免费鲁丝| 国产亚洲av片在线观看秒播厂| 国产精品av久久久久免费| 多毛熟女@视频| 侵犯人妻中文字幕一二三四区| 看免费成人av毛片| 免费av中文字幕在线| 久久久a久久爽久久v久久| 日本wwww免费看| 飞空精品影院首页| 26uuu在线亚洲综合色| 精品国产超薄肉色丝袜足j| 边亲边吃奶的免费视频| 男人爽女人下面视频在线观看| 亚洲人成77777在线视频| 久久国产亚洲av麻豆专区| 欧美人与善性xxx| 男女边吃奶边做爰视频| 久久国产精品男人的天堂亚洲| 色婷婷av一区二区三区视频| 亚洲图色成人| 搡女人真爽免费视频火全软件| 另类精品久久| 18在线观看网站| 国产黄色视频一区二区在线观看| 天天操日日干夜夜撸| 超碰成人久久| 国产免费福利视频在线观看| 亚洲国产精品成人久久小说| 大话2 男鬼变身卡| 中文乱码字字幕精品一区二区三区| 国产熟女欧美一区二区| 美国免费a级毛片| 国产免费现黄频在线看| 一级毛片我不卡| 欧美最新免费一区二区三区| 国产免费视频播放在线视频| videosex国产| 欧美日韩国产mv在线观看视频| 国产白丝娇喘喷水9色精品| 人人妻人人添人人爽欧美一区卜| 九草在线视频观看| 日本爱情动作片www.在线观看| 一本一本久久a久久精品综合妖精 国产伦在线观看视频一区 | 飞空精品影院首页| 日韩不卡一区二区三区视频在线| www.精华液| 色婷婷av一区二区三区视频| 免费在线观看视频国产中文字幕亚洲 | 人人澡人人妻人| 91成人精品电影| 只有这里有精品99| 一本大道久久a久久精品| 免费在线观看完整版高清| 99热网站在线观看| 亚洲成人一二三区av| 天堂中文最新版在线下载| 久久久久久久久免费视频了| 日本欧美视频一区| 亚洲国产av影院在线观看| 秋霞在线观看毛片| 国产成人精品久久久久久| 国精品久久久久久国模美| 男女无遮挡免费网站观看| 久久久久久伊人网av| 伊人久久国产一区二区| 中文字幕色久视频| 久久这里有精品视频免费| 免费av中文字幕在线| 热99久久久久精品小说推荐| 我的亚洲天堂| 看十八女毛片水多多多| 亚洲精品国产av成人精品| 欧美xxⅹ黑人| 一级a爱视频在线免费观看| 国产黄色免费在线视频| 婷婷成人精品国产| 国产精品秋霞免费鲁丝片| 久久精品国产鲁丝片午夜精品| 男人操女人黄网站| av国产精品久久久久影院| 在线观看一区二区三区激情| 亚洲第一区二区三区不卡| av一本久久久久| 亚洲少妇的诱惑av| 久久精品亚洲av国产电影网| 老司机亚洲免费影院| 性高湖久久久久久久久免费观看| 在线观看美女被高潮喷水网站| 国产又爽黄色视频| 搡女人真爽免费视频火全软件| 韩国av在线不卡| 成年美女黄网站色视频大全免费| 免费观看无遮挡的男女| 18禁国产床啪视频网站| 日韩中文字幕视频在线看片| 如何舔出高潮| 男女边摸边吃奶| 咕卡用的链子| 18+在线观看网站| 色吧在线观看| 亚洲国产成人一精品久久久| 最新中文字幕久久久久| 日本91视频免费播放| 成人国产av品久久久| 国产乱人偷精品视频| 女人精品久久久久毛片| 男人添女人高潮全过程视频| 国产片内射在线| 亚洲,欧美精品.| 天美传媒精品一区二区| 人人妻人人澡人人爽人人夜夜| 午夜福利影视在线免费观看| 男女免费视频国产| 国产黄色视频一区二区在线观看| 亚洲熟女精品中文字幕| 老熟女久久久| 在线观看三级黄色| a级片在线免费高清观看视频| 国产日韩一区二区三区精品不卡| 亚洲中文av在线| 久久午夜福利片| 欧美日韩一区二区视频在线观看视频在线| 水蜜桃什么品种好| 黄片无遮挡物在线观看| 久久久久久人妻| 成人国产麻豆网| 自线自在国产av| 欧美日韩视频精品一区| 国产成人免费无遮挡视频| 黄色怎么调成土黄色| 国产亚洲av片在线观看秒播厂| 免费人妻精品一区二区三区视频| 婷婷色综合www| 亚洲成色77777| 久久久久久久精品精品| 精品视频人人做人人爽| av又黄又爽大尺度在线免费看| 伊人久久国产一区二区| 国产精品一国产av| 国产黄色视频一区二区在线观看| 国产av码专区亚洲av| 夫妻午夜视频| 日韩视频在线欧美| 免费播放大片免费观看视频在线观看| 人妻系列 视频| 在线看a的网站| 午夜老司机福利剧场| av有码第一页| 综合色丁香网| 日韩在线高清观看一区二区三区| 一级片'在线观看视频| 乱人伦中国视频| 五月伊人婷婷丁香| 韩国高清视频一区二区三区| 久久免费观看电影| 久久久久网色| 欧美精品一区二区大全| 久久精品久久久久久久性| 国产欧美日韩综合在线一区二区| 免费黄频网站在线观看国产| 多毛熟女@视频| 亚洲成av片中文字幕在线观看 | 伊人久久国产一区二区| 亚洲综合色网址| 一本一本久久a久久精品综合妖精 国产伦在线观看视频一区 | 久久久久久久亚洲中文字幕| 久久ye,这里只有精品| 看免费成人av毛片| 免费日韩欧美在线观看| 亚洲av国产av综合av卡| av线在线观看网站| 黑人猛操日本美女一级片| 91精品三级在线观看| 一本久久精品| 国产黄色免费在线视频| 久久精品国产a三级三级三级| 777米奇影视久久| 深夜精品福利| 日韩欧美精品免费久久| freevideosex欧美| www.自偷自拍.com| 2018国产大陆天天弄谢| 十八禁网站网址无遮挡| 欧美国产精品va在线观看不卡| 国产极品天堂在线| 97在线人人人人妻| 男女高潮啪啪啪动态图| 国产成人精品在线电影| 丝袜脚勾引网站| av福利片在线| 日韩精品免费视频一区二区三区| 黄片播放在线免费| 国产有黄有色有爽视频| 国产亚洲一区二区精品| 美女国产视频在线观看| 蜜桃在线观看..| 毛片一级片免费看久久久久| 中文天堂在线官网| 免费黄网站久久成人精品| 精品久久蜜臀av无| 欧美老熟妇乱子伦牲交| 人妻人人澡人人爽人人| 亚洲av国产av综合av卡| 十八禁高潮呻吟视频| 夫妻午夜视频| 精品酒店卫生间| 国产精品久久久久久精品电影小说| 91国产中文字幕| 午夜福利视频在线观看免费| 青春草亚洲视频在线观看| 亚洲人成77777在线视频| 亚洲精品第二区| 亚洲美女视频黄频| 国产又色又爽无遮挡免| 精品卡一卡二卡四卡免费| 国产精品 国内视频| 999久久久国产精品视频| 大片电影免费在线观看免费| 十八禁网站网址无遮挡| 国产精品熟女久久久久浪| 一区在线观看完整版| 天天躁狠狠躁夜夜躁狠狠躁| 美女xxoo啪啪120秒动态图| 中文字幕另类日韩欧美亚洲嫩草| 一区二区三区激情视频| 久久久久视频综合| 国产精品二区激情视频| 美国免费a级毛片| 黄片无遮挡物在线观看| 欧美av亚洲av综合av国产av | 999精品在线视频| 成人国语在线视频| 国产成人一区二区在线| 免费在线观看视频国产中文字幕亚洲 | 久久毛片免费看一区二区三区| 亚洲av福利一区| 日韩精品免费视频一区二区三区| 有码 亚洲区| 午夜免费观看性视频| 青春草亚洲视频在线观看| 深夜精品福利| 久久97久久精品| 久久久久久久久久久免费av| av电影中文网址| 亚洲欧美一区二区三区黑人 | 寂寞人妻少妇视频99o| 女性被躁到高潮视频| 永久免费av网站大全| 少妇熟女欧美另类| 国产精品偷伦视频观看了| 婷婷成人精品国产| 免费在线观看黄色视频的| 久久精品国产a三级三级三级| 爱豆传媒免费全集在线观看| 免费少妇av软件| 午夜久久久在线观看| 国产av一区二区精品久久| 黑人猛操日本美女一级片| 国产成人一区二区在线| 啦啦啦在线免费观看视频4| 久久久国产精品麻豆| 亚洲综合精品二区| 亚洲精品aⅴ在线观看| 欧美成人午夜精品| 哪个播放器可以免费观看大片| 久久久久久久大尺度免费视频| 亚洲美女视频黄频| 久久久国产欧美日韩av| 精品一区二区免费观看| 免费黄频网站在线观看国产| 啦啦啦在线观看免费高清www| 成人午夜精彩视频在线观看| 美女xxoo啪啪120秒动态图| 日本黄色日本黄色录像| 黄色毛片三级朝国网站| 最近中文字幕2019免费版| 下体分泌物呈黄色| 国产精品国产三级专区第一集| 丝袜在线中文字幕| 女人精品久久久久毛片| 久久久精品免费免费高清| 日韩成人av中文字幕在线观看| 国产成人精品福利久久| 午夜老司机福利剧场| av网站免费在线观看视频| 国产片特级美女逼逼视频| 18在线观看网站| 精品99又大又爽又粗少妇毛片| 亚洲av男天堂| 国产又爽黄色视频|