• <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 ?

    A Comparative Study of Friction Self-Piercing Riveting and Self-Piercing Riveting of Aluminum Alloy AA5182-O

    2021-04-22 11:35:00YunwuMaHeShanSizheNiuYongbingLiZhongqinLinNinshuMa
    Engineering 2021年12期

    Yunwu Ma, He Shan, Sizhe Niu, Yongbing Li,*, Zhongqin Lin, Ninshu Ma

    a Shanghai Key Laboratory of Digital Manufacture for Thin-Walled Structures, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

    b State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

    c Joining and Welding Research Institute, Osaka University, Osaka 567-0047, Japan

    Keywords:Self-piercing riveting Friction self-piercing riveting Mechanical joining Quasi-static strength Fatigue

    ABSTRACT In this paper, self-piercing riveting (SPR) and friction self-piercing riveting (F-SPR) processes were employed to join aluminum alloy AA5182-O sheets. Parallel studies were carried out to compare the two processes in terms of joint macrogeometry, tooling force, microhardness, quasi-static mechanical performance, and fatigue behavior. The results indicate that the F-SPR process formed both rivet–sheet interlocking and sheet–sheet solid-state bonding, whereas the SPR process only contained rivet–sheet interlocking. For the same rivet flaring, the F-SPR process required 63% less tooling force than the SPR process because of the softening effect of frictional heat and the lower rivet hardness of F-SPR. The decrease in the switch depth of the F-SPR resulted in more hardening of the aluminum alloy surrounding the rivet. The higher hardness of aluminum and formation of solid-state bonding enhanced the F-SPR joint stiffness under lap-shear loading, which contributed to the higher quasi-static lap-shear strength and longer fatigue life compared to those of the SPR joints.

    1. Introduction

    The implementation of light alloys in automotive body manufacturing is a strategic approach to improve fuel efficiency. This,together with the lightweight demand of electric vehicle bodies to improve the battery range, has driven automotive manufacturers worldwide to replace traditional steel parts with an increasing amount of aluminum alloys,raising the demand for aluminum spot joining.

    Resistance spot welding(RSW)is a high-reliability and low-cost technology extensively used in traditional steel vehicle body assembly. However, the RSW of aluminum alloys faces several critical issues.Aluminum alloys have a higher thermal conductivity,electrical conductivity, specific heat, and latent heat than steel;thus,they require a larger quantity of resistive heating in a shorter time and therefore a much higher welding power requirement than the steel RSW process [1]. Additionally, aluminum RSW is subjected to rapid electrode cap wear due to the nonuniform and nonconducting oxide film on the aluminum surface that generates excessive heat around the electrodes [2]. Another key issue of aluminum RSW lies in the strength loss after welding (i.e., the so-called thermal softening effect) due to the dissolution of precipitates at high welding temperatures [3]. Improved RSW techniques,such as RSW using multi-ring domed(MRD)electrodes[4,5]and the DeltaSpot RSW process using specially designed tapes between the electrode cap and the aluminum workpiece [6], have been proven capable of alleviating oxide film problems and balancing the heat distribution during RSW.

    Mechanical fastening methods, such as clinching, self-piercing riveting(SPR)and flow drill screwing(FDS),have been extensively used to fabricate aluminum-intensive vehicle bodies. SPR possesses high joining strength, short cycle time, and no thermal effects [7–9], making it the most preferred alternative to the aluminum RSW process, especially for load-bearing structures in a body-in-white. Numerous studies have been published in the past two decades to investigate the formation and performance of aluminum SPR joints. Xu [10] investigated the effects of rivet and die profiles on the physical attributes of SPR joints. Huang et al. [11]studied the riveting-induced distortion to the SPR joints of AA5182-H11 aluminum alloy sheets. The influences of the clamping force, blank holder size, and sheet width/length on the local distortion of the SPR joint were revealed,and process optimization was conducted to minimize the local distortion. Zhao et al. [12]investigated the effects of workpiece thickness on the fatigue performance of SPR joints.They observed a transfer of the fatigue failure position from the upper workpiece to the lower workpiece with increasing sheet thickness. He et al. [13] also reported the transfer of fatigue failure position in an SPR joint as a result of the increased joint stiffness. Zhang et al. [14] pointed out that the fatigue failure of SPR joints was highly relevant to fretting damage,the location of which changed from the interface between the rivet tip and lower sheet to the interface between the upper and lower sheets with a decrease in the load. Li [15] investigated the influence of aluminum surface conditions on the SPR joint strength of AA5754. He reported that grit blasting or sandpaper grounding increased the surface roughness of the aluminum sheet and increased the resistance of rivet slip-out from the lower sheet,which enhanced the lap-shear strength of the aluminum SPR joints.

    Research and application of the SPR process in 5xxx and 6xxx series aluminum alloys have already been successfully and comprehensively performed. However, cracking, which deteriorates the joint mechanical performance to a great extent, is inevitable when riveting low ductility metals, such as cast aluminum, 7xxx series aluminum alloys, and magnesium alloys, due to the large localized plastic deformation that sheet materials undergo. Preheating of the workpieces via laser [16], resistance heating [17],or induction heating [18] methods before SPR has been adopted to improve the formability of materials and inhibit cracking.However, all these preheating methods require add-on tools and thereby lead to increased process costs and cycle times.

    Li et al. [19] invented a friction self-piercing riveting (F-SPR)process to cope with the cracking problem for riveting lowductility metals.By converting the feeding motion of a rivet during the SPR process into a hybrid motion of feeding and rotating,the FSPR process generates local frictional heat to soften the surrounding metals. Since the F-SPR process generates heat by the rotation of the rivet, the high cost and long cycle time spent on preheating are eliminated.Liu et al.[20]achieved crack-free joining of magnesium alloy AZ31B and aluminum alloy AA7075-T6 by F-SPR. Ma et al. [21] improved the F-SPR joint performance by introducing a two-stage strategy,which fed the rivet slowly with rapid spinning in the first stage for heat generation and then quickly without spinning in the second stage for rivet flaring. This two-stage strategy successfully improved the lap-shear strength of friction selfpiercing riveted aluminum alloy and magnesium alloy joints by 30%. Moreover, as a byproduct of the stir motion of the rivet,solid-state bonding forms at the sheet/sheet interfaces in F-SPR joints, providing another enhancement in addition to mechanical interlocking. Similar combinations of mechanical joining and metallurgical/adhesive bonding were reported by Huang et al.[22,23] and Meng et al. [24] for aluminum-to-steel as well as metal-to-polymer joints.

    To date, all the studies published regarding F-SPR have focused on low-ductility materials. It is no doubt that the F-SPR joints in low-ductility materials,where cracking is eliminated,have a better load-bearing capacity than the SPR joints that show visible cracking. However, the comparisons between these two processes are hardly fair. There is a gap in the existing body of work because a comprehensive comparison between SPR and F-SPR processes has not yet been provided.

    In this paper,an AA5182-O aluminum alloy,which is not classified as a low ductility metal and can be soundly riveted by the SPR process without cracking, was selected for a back-to-back competition between the SPR and F-SPR processes.Comparisons between the two processes were carried out in terms of joint macrogeometry, tooling force, microhardness, quasi-static mechanical behavior, and fatigue performance.

    2. Experimental details

    2.1. Materials

    Commercial automotive-grade AA5182-O aluminum alloys with thicknesses of 1.5 and 2.0 mm were used as the upper layer(rivet side)and lower layer(die side),respectively.Table 1 presents the mechanical properties of the AA5182-O aluminum alloy.

    2.2. Process procedures and parameters

    As shown in Fig.1,the SPR process was performed by punching a semi-hollow rivet against sheet workpieces, which were supported by a matching die. While penetrating through the upper sheet,the rivet shank flared plastically to interlock the workpieces.Pip dies are mainly used for joining soft materials(e.g.,5xxx series aluminum alloy)to increase rivet flaring[25].In a servo-driven SPR process, the tooling velocity that determines the initial kinetic energy of the rivet is adjusted to control the rivet insertion depth in the workpieces. A flush set down of the rivet head in the upper sheet is always treated as a target for a trial of the tooling velocity[26].

    The F-SPR process starts with driving a rivet,rotating it at a high speed,and feeding it slowly in stage I for frictional heat generation and workpiece softening. Then, in stage II, the spinning is stopped and it is fed quickly to achieve rivet flaring,as shown in Fig.2[27].Stages I and II are also known as the friction softening stage and the punch riveting stage,respectively.Therefore,the F-SPR process parameters include two feed rates, one rotational speed, and one switch depth for the two stages.If the two feed rates and rotational speed are fixed,a smaller switch depth results in less friction heat generation and thereby a larger force to flare the rivet shank but raises the risk of material cracking or rivet buckling owing toinsufficient softening of the workpieces.In contrast,a larger switch depth corresponds to a higher friction heat generation that is helpful for material softening but at the cost of compromising rivet flaring. If the switch depth is set to zero, the F-SPR process turns into the traditional SPR process.

    Table 1 Mechanical properties of the AA5182-O aluminum alloy.

    Fig. 1. Schematic of the SPR process: (a) positioning, (b) rivet piercing the upper sheet, (c) rivet setting down, and (d) tooling retreat.

    Fig.2. Schematic of the F-SPR process:(a)positioning,(b)friction softening,(c)quick stopping,(d)punch riveting,and(e)tooling retreat.f1,f2:rivet feed rates of stage I and stage II,respectively;ω1:rotational speed of stage I;Dswitch:switch depth;Dplunge:constant rivet plunge depth.Reproduced from Ref.[27]with permission of Elsevier,?2020.

    For a given stack of sheets, various rivet and die combinations can be used to produce an SPR joint, among which an optimum selection is determined via an evaluation of the cross-section geometries.In this study,preliminary work was performed to optimize the rivet and die for the studied sheet stack according to the SPR evaluation indexes in the vehicle industry[28].The optimized steel countersunk rivet had a hardness of 483 Vickers hardness(HV) and a mass of approximately 0.6 g, as shown in Fig. 3. The pip die had a 9.0 mm cavity diameter and 2.0 mm depth,as shown in Fig.4.A tooling velocity of 220 mm·s-1was used to achieve flush set down of the rivet cap in the upper sheet. The cycle time of the SPR process was approximately 0.05 s.

    Fig.3 shows the dimensions of the friction self-piercing rivet.A patented rivet head design was adopted to ensure reliable rotational driving [29]. The rivet head included six equally spaced notches for torque transmission and a center positioning hole.Since the rivet for the F-SPR process had an axisymmetrical body and a nonaxisymmetrical head, the rivet cross-sections may differ in the head profile. Fig. 5 shows the three-dimensional model and three typical cross-sectional profiles of the friction self-piercing rivet. Except for the rivet head design, the other dimensions of the rivet for the F-SPR process were completely comparable to those for SPR. The rivet for F-SPR has a hardness of 255 HV, much softer than the rivets for SPR. The mass of the rivet for the F-SPR process was approximately 0.9 g, which is 50% heavier than that for SPR due to the additional rivet head structures. A pip die with a 9.0 mm cavity diameter and 1.7 mm depth was used for the FSPR process.

    Fig.3. Physical images and dimensions of the rivets:(a)SPR and(b)F-SPR.The unit is millimeter.

    Fig. 4. Dimensions of the pip die in the SPR and F-SPR processes. The unit is millimeter. H: die depth.

    Fig. 5. Three-dimensional model and three typical cross-section profiles of the friction self-piercing rivet.

    Table 2 F-SPR process parameter combinations and the corresponding energy inputs.

    The F-SPR process was performed on a customized machine equipped with two servo motors,which accounted for the feeding and spinning motions. In all the F-SPR experiments, a constant rivet plunge depth (Dplunge) of 5.3 mm was applied. The rivet feed rate(f1)and rotational speed(ω1)of stage I and the rivet feed rate(f2)of stage II were also set as constants,leaving the switch depth(Dswitch) as the only variable. Table 2 lists the detailed process parameter sets and the corresponding cycle times. An increase in Dswitchresulted in additional process time being spent on the friction softening of the work materials and therefore a longer total cycle time. When Dswitchwas set equal to Dplunge, the process contained only stage I, as shown for F-SPR_1 in Table 2.

    The energy input during F-SPR can be quantified as

    where E is the energy input,f is the rivet feed rate,F is the reactive force, M is the reactive torque, t is time,ω is rotational speed, and Δt is the process time.The calculated energy inputs using the measured tooling force and driving torque under various process parameters are listed in Table 2. As expected, the energy input increased with Dswitch.

    2.3. Cross-section observation and microhardness testing

    The as-fabricated SPR and F-SPR joints were cross-sectioned,mechanically ground, polished to a surface finish of 0.03 μm, and observed with a Leica DM6M optical microscope (LEICA Microsystems,Germany).Microhardness measurements of aluminum sheet materials around the rivet were conducted on a Wilson VH1102 hardness tester (Buehler, USA) with a 0.2 mm pitch, 50 g load,and 10 s dwell time.

    2.4. Mechanical tests

    Quasi-static lap-shear tests of the SPR and F-SPR joints were conducted at 3.0 mm·min-1stroke speed on a SUNS UTM5540X tensile machine (SUNS, China). The peak load and energy absorption presented in this paper were averaged from three repetitive tests. Load-controlled fatigue tests were performed for the riveted joints at 20 Hz on a closed-loop MTS servo-hydraulic test frame(MTS Systems Corporation, USA) under tension–tension mode. A sinusoidal waveform with a constant amplitude was applied. The ratio of the minimum load to the maximum load, known as the load ratio R, was 0.1. Termination of the fatigue test was triggered by either the occurrence of visible cracks or the cycle count reaching two million.

    The same specimen configuration and grip distance were used during the quasi-static and fatigue tests,as shown in Fig.6.During the tests, spacers with appropriate thicknesses were attached to both ends of the specimen to avoid undesirable bending effects.

    3. Results and discussion

    3.1. Joint macroscopic profile and tooling force

    Fig. 7 shows the macroscopic profile of an SPR joint. The rivet shank penetrated through the upper sheet and flared into the lower sheet without any cracking or gap defects, forming a sound joint. An interface was presented between the trapped aluminum and the lower sheet. The rivet flaring of the SPR joint, defined as the diameter of the rivet shank tip in the final joint,was 6.24 mm.

    Fig.8 presents the macroscopic profiles of the F-SPR joint under four different process parameter sets. The joint macroscopic profiles differed significantly for various Dswitchvalues. For F-SPR_1,where Dswitch=5.3 mm,obvious defects occurred,including a large void close to the rivet tip and a sharp notch at the joint bottom.Moreover,apparent burrs were formed near the flange of the rivet head, as shown in Fig. 8(a). The size of the void at the rivet tip decreased with a reduction in the Dswitchvalue and diminished completely at a Dswitchof 2.0 mm (F-SPR_4), as shown in Fig. 8(d).The sharp notch at the rivet tip and the burrs near the rivet head flange were also eliminated for a Dswitchsmaller than 4.0 mm, as shown in Figs. 8(c) and (d). Moreover, the rivet flaring increased with a reduction in Dswitch(i.e.,from F-SPR_1 to F-SPR_4),as shown in Fig. 9.

    Fig. 6. Dimensions of lap-shear and fatigue testing samples. The unit is millimeter.

    Fig. 7. Macroscopic profile of an SPR joint.

    The variation of the F-SPR joints with Dswitchcan be explained as follows.The F-SPR process under Dswitch=5.3 mm(F-SPR_1),corresponding to the highest heat input among the studied process parameter sets, resulted in an overheating and oversoftening condition of the aluminum adjacent to the rivet.Therefore,less deformation resistance acted on the rivet. The rivet tip only deformed slightly, creating the smallest rivet flaring, as shown in Fig. 9.Moreover, as the oversoftened aluminum surrounding the rivet tip had high fluidity, it flowed almost freely to the die cavity with the feeding of the rivet, leaving a large void at the rivet tip and forming a sharp notch at the joint bottom, as shown in Fig. 8(a).With a reduction in Dswitch, the generated heat decreased. Consequently, the increased deformation resistance of the aluminum sheets resulted in greater rivet flaring, as shown in Fig. 9. When Dswitchdecreased to 3.0 or 2.0 mm, the heat generation decreased significantly, and the aluminum material was not able to flow freely like it did under a larger Dswitch; instead, it was pushed by the greatly flared rivet tip and curved down towards the wall of the die cavity. As a result, void and sharp notch defects were eliminated. The curved interfaces in the joints from F-SPR_3(Dswitch= 3.0 mm) and F-SPR_4 (Dswitch= 2.0 mm) support this explanation, as shown in Figs. 8(c) and (d).

    The burrs near the rivet head flange in the F-SPR_1(Dswitch= 5.3 mm) and F-SPR_2 (Dswitch= 4.0 mm) joints were produced by the rotational motion of the rivet. In stage I of the F-SPR process, the aluminum materials close to the rivet tip were softened to a high-fluidity condition and squeezed by the rivet shank to flow towards the upper sheet surface, forming burrs.For the F-SPR_3 (Dswitch= 3.0 mm) and F-SPR_4 (Dswitch= 2.0 mm)joints, however, the relatively lower heat input and the bending effect of the sheets successfully inhibited the formation of burrs.

    It is noteworthy that in all four F-SPR joints, the aluminum interfaces near the rivet outer surface and inside the rivet shank diminished, indicating that solid-state bonding formed between the aluminum alloy sheets, as shown in Fig. 8. The solid-state bonding inside the rivet cavity did not change with the applied F-SPR process parameters. However, the solid-state bonding area outside the rivet decreased with a decrease in Dswitchdue to a reduction in the heat input.

    Fig. 10 compares the peak tooling forces required to finish the SPR and F-SPR processes.The peak tooling force of the SPR process was more than 40 kN. However, the F-SPR process required more than a 50% lower tooling force. From F-SPR_1 to F-SPR_4, an increase in the peak tooling force was observed with a decrease in Dswitchowing to the decreased energy input. This increase in tooling force resulted in increased rivet flaring.One can notice that the F-SPR_3 (Dswitch= 3.0 mm) joint showed a similar rivet flaring but required 63% less tooling force compared to that for the SPR joint, as marked by red dashed boxes in Figs. 9 and 10. This can be attributed to the softening effect of friction heat and the lower rivet hardness of F-SPR. It is noteworthy that the SPR and F-SPR processes have different requirements for rivets to reach the desired rivet flaring. The rivet in the SPR process is subjected to greater resistance from the workpieces. A harder rivet is required to avoid rivet buckling or rivet failure during the SPR process.However, the workpieces in the F-SPR process are softened by friction heat. As a result, the rivet is subjected to less feeding resistance and is less likely to flare during the F-SPR process. Therefore, a softer rivet is necessary for the F-SPR process to achieve the desired rivet flaring. A reduction in the F-SPR tooling force can result in lower wear rates of the riveting tool and the die, lower required C-frame stiffness and lower required capacity of servo motors of the riveting gun,and less residual stress in the joints.All these factors can help reduce the process cost and increase the process reliability.

    3.2. Microhardness distribution

    In an SPR joint,the workpiece materials adjacent to the rivet are subjected to local work hardening because of the intense plastic deformation. However, in an F-SPR joint, the work materials adjacent to the rivet are subjected to both work hardening and thermal softening,making the strength variation of the work material complex. Fig. 11 shows the microhardness distribution of the workpiece materials in the SPR and the F-SPR joints.

    Fig. 8. Macroscopic profiles of the F-SPR joint under four different process parameter sets: (a) F-SPR_1 (Dswitch = 5.3 mm), (b) F-SPR_2 (Dswitch = 4.0 mm), (c) F-SPR_3(Dswitch = 3.0 mm), and (d) F-SPR_4 (Dswitch = 2.0 mm).

    Fig. 9. Rivet flaring of the SPR and the F-SPR joints.

    Fig. 10. Peak tooling force of the SPR and F-SPR processes.

    The hardness of the AA5182-O base material is 79 HV.As shown in Fig.11(a),the aluminum in the SPR joint hardened due to a large plastic deformation.Aluminum located adjacent to the rivet shank and below the rivet tip,where plastic deformation was severe,had a relatively higher hardness.The highest hardness in the SPR joint reached 136 HV. For the F-SPR joint with Dswitch= 5.3 mm (FSPR_1), as shown in Fig. 11(b), the aluminum hardness close to the rivet shank and below the rivet tip increased slightly, and the highest hardness was only 98 HV. This is because the high frictional heat input caused material softening, which partially compensated for the work hardening due to plastic deformation.With a decrease in Dswitch, the thermal softening effect weakened.Moreover, the high-rate feeding of the rivet in stage II of the F-SPR increased the degree of work hardening on the workpiece material. As a consequence, the overall hardness of aluminum sheets increased with a decrease in Dswitch, referring to Figs. 11(c)–(e). To this end, it can be concluded that using a small Dswitchin the F-SPR process is beneficial to alleviate the negative effect of thermal softening.

    3.3. Quasi-static mechanical performance

    Fig. 12 compares the lap-shear strength and energy absorption of the SPR and F-SPR joints in quasi-static lap-shear tests.As shown in Fig. 12, the F-SPR joint with Dswitch= 5.3 mm had the lowest strength and energy absorption because of its smallest rivet flaring among all the joints. For the rest of the F-SPR joints, a higher strength and energy absorption than those for the SPR joints were achieved. The joint for F-SPR_3, which had a rivet flaring value similar to that for the SPR joint, showed a 25.1% and 43.5% higher lap-shear strength and energy absorption, respectively, than the SPR joint.

    Fig. 13 shows the lap-shear load–displacement curves of the SPR and the F-SPR joints.For the SPR joint and the F-SPR joint with Dswitch= 5.3 mm (F-SPR_1), yielding occurred earlier, and rivet pull-out mode was presented, as shown in Fig. 14(a). The rest of the F-SPR joints yielded at higher loads, and the corresponding failure mode was upper sheet fracture, as shown in Fig. 14(b).The load–displacement curves from 2.0 to 3.5 kN are magnified and shown in Fig. 13. The joints for F-SPR_2–4 exhibited higher stiffness than the F-SPR_1 and the SPR joints before yielding. The improved strength and stiffness of the F-SPR joints were due to the larger rivet flaring, higher hardness of aluminum surrounding the rivet,and the formation of solid-state bonding.The upper sheet fracture mode indicates that the mechanical interlocking between the rivet and the sheet was strong enough to bear the lap-shear load,and the upper sheet surrounding the rivet became the weakest part of the joint. The occurrence of upper sheet fracture indicates that the strength of the joint almost reached its upper limit.

    3.4. Fatigue performance

    Among the four F-SPR joints processed with different parameters,F-SPR_3 had the closest rivet flaring as well as hardness distribution compared to those for the SPR joint.Therefore,F-SPR_3 was selected for comparison of the fatigue performance with the SPR joint. The fatigue results are listed in Table 3 and plotted as the load amplitude(S)versus the number of cycles to failure(N),which are known as S–N curves, as shown in Fig. 15.

    Fig.11. Microhardness distribution of the workpiece materials in the SPR and F-SPR joints:(a)SPR,(b)F-SPR_1(Dswitch =5.3 mm),(c)F-SPR_2(Dswitch =4.0 mm),(d)F-SPR_3(Dswitch = 3.0 mm), and (e) F-SPR_4 (Dswitch = 2.0 mm). BM: base material.

    Fig. 12. Lap-shear strength and energy absorption of the SPR and F-SPR joints.

    Fig. 13. Lap-shear load–displacement curves of the SPR and the F-SPR joints.

    Fig.14. Lap-shear failure modes of the SPR and the F-SPR joints:(a)rivet pull-out of the SPR joint and (b) upper sheet fracture of the F-SPR_3 (Dswitch = 3.0 mm) joint.

    From the S–N curves the load amplitudes corresponding to 105fatigue life are calculated to be 2.82 and 3.34 kN for SPR and F-SPR,respectively. Similarly, the load amplitudes corresponding to 106fatigue life are 2.14 and 2.45 kN for SPR and F-SPR, respectively.Therefore, the F-SPR joints presented 18.4% and 14.5% higher loadamplitudes for the 105and 106fatigue lives, respectively, compared to those of the SPR joints. For both joints, the fatigue lives were extended with a decrease in the load amplitude. Nevertheless, the F-SPR joint had longer fatigue lives than the SPR joint.The SPR joint with both high (3.0 kN) and low (2.5 kN) load amplitudes and the F-SPR joint with a high load amplitude (3.2 kN) failed in the upper sheet next to the rivet cap, as shown in Figs. 16(a) and (b). However, the F-SPR joint at a low load amplitude (2.7 kN) failed in the lower sheet near the rivet tip, as shown in Figs. 16(c) and (d).

    Table 3 Fatigue results of the SPR and F-SPR_3 joints.

    Fig. 15. S–N curves of the SPR and the F-SPR joints. The black arrows indicate that the fatigue test terminated after two million cycles without failure.

    A similar upper sheet fatigue failure location in the aluminum SPR joint was reported by Li et al. [30]. The upper sheet failure mode was attributed to the occurrence of cyclic secondary bending, which resulted in a stress concentration near the rivet head and further accelerated fretting damage as well as the development of fatigue cracks in the upper sheet. In this study, the secondary bending of the upper sheet was greater due to its reduced thickness compared to that of the lower sheet.As a result,fretting occurred at the interface between the two sheets, as demonstrated by the area with dark fretting debris marks in Fig.16(b).The SPR joint with a 2.5 kN load amplitude corresponded to less secondary bending compared to that for a 3.0 kN load amplitude; therefore, the number of cycles was increased before fatigue failure.

    Fig. 16. Crack locations after fatigue tests: (a, b) SPR joint at a 2.5 kN load amplitude and (c, d) F-SPR_3 joint at a 2.7 kN load amplitude.

    Fig.17. Fracture surfaces of the SPR joint at a 2.5 kN load amplitude:(a) magnified view of the fracture surface of the upper sheet, (b) scanning electron microscope (SEM)image of location b in (a) showing transgranular fracture, and (c) SEM image of location c in (a) showing ductile fracture.

    Fig.17 presents the fracture surfaces of the SPR joint at a 2.5 kN load amplitude. As shown in Fig. 17, the central region, roughly underneath the rivet cap, exhibited cleavage fracture. The typical cleavage steps in Fig. 17(b) corresponded to brittle transgranular fracture, indicating the initiation of fatigue cracks adjacent to the rivet cap.The region near the sheet edge exhibited dimple fracture,as shown in Fig.17(c),which is indicative transient ductile fracture when a local stress exceeds the bearing limit of the remaining structure. To this end, the fracture path in the upper sheet can be conjectured as being from a crack initiating in the region near the rivet cap due to fretting wear and propagating along the sheet width direction until complete fracture.

    Similarly, the F-SPR joint at a load amplitude of 3.2 kN also failed in the upper sheet due to fretting damage. The F-SPR joint exhibited a higher stiffness than the SPR joint, as indicated by the shorter displacement of the F-SPR_3 joint at a 3.2 kN lapshear load than the SPR joint with a 3.0 kN load, as shown in Fig. 13. Therefore, less secondary bending was induced in the F-SPR joint under the cyclic fatigue load, resulting in a larger number of cycles before fatigue failure.

    For the F-SPR joint at a 2.7 kN load amplitude, the decrease in the load amplitude reduced the bending effect and changed the fracture location from the upper sheet to the lower sheet.Fig. 18 shows the microstructures on the surface of the rivet shank and the fractured lower sheet. Due to fretting wear in the faying interface between the rivet and the lower sheet, the materials on the sheet surface were scratched, oxidized, and stuck to the rivet shank. Moreover, local fretting also caused cracking of the rivet shank. Therefore, the rivet shank that contacted the lower sheet exhibited a continuous crack and a rough surface covered with fretting debris, as shown in Figs. 18(c) and(d). On the fracture surface of the lower sheet near the rivet tip in Fig. 18(e), transgranular fracture with secondary cracks and fatigue striations were present, indicating the propagation of fatigue cracks in this region. Thus, the fatigue failure of the F-SPR joint was due to the fretting between the rivet and the lower sheet, which caused the fatigue crack to develop in the lower sheet near the rivet tip and propagate along the thinnest area at the joint bottom where a notch was present,as shown in Fig. 19.

    Fig. 18. Fracture surfaces of the F-SPR_3 joint at a 2.7 kN load amplitude: (a) close-up view of the fractured sample; (b) SEM image of location b in (a) showing the rivet surface and lower sheet;(c,d)SEM images of locations c and d in(b)showing crack and fretting debris on the rivet surface,respectively;and(e)SEM image of location e in(b)showing transgranular fracture in the lower sheet.

    Fig. 19. Fretting and cracking locations in the F-SPR and the SPR joints at low load amplitudes.

    Although the F-SPR_3 and the SPR joints had a similar rivet flaring, the stronger stiffness of the F-SPR_3 joint enhanced the resistance to secondary bending during the fatigue test, which delayed the fretting damage in the upper sheet.However,the presence of a notch at the F-SPR joint bottom became a short slab,hindering the further improvement of the high cycle fatigue performance. In future work, process optimization is necessary to eliminate the notch in the F-SPR joint and increase the wall thickness of the lower sheet surrounding the rivet tip.

    4. Conclusions

    This body of work applied both SPR and F-SPR processes to join 1.5–2.0 mm-thick AA5182-O aluminum alloy sheets. Comparative studies were carried out to systematically evaluate the two processes in terms of joint macrogeometry, tooling force, microhardness distribution, quasi-static lap-shear performance, and fatigue behavior. The following conclusions can be drawn:

    (1) The SPR joint was formed by rivet–sheet interlocking,whereas the F-SPR joint contained both rivet–sheet interlocking and sheet–sheet solid-state bonding. The F-SPR joint created with a 3.0 mm switch depth exhibited a similar rivet flaring but required 63% lower tooling force compared to that for the SPR joints because of frictional heat softening and the lower FSPR rivet hardness.

    (2) The F-SPR joint exhibited an increased aluminum hardness with decreasing switch depth. The F-SPR joint made with switch depths smaller than 4.0 mm increased the hardening of the aluminum surrounding the rivet, which compensated for the softening due to the heat effect and produced a higher overall hardness than that in the SPR joints.

    (3) Due to the higher hardness of aluminum and the formation of solid-state bonding,the F-SPR joint with a 3.0 mm switch depth exhibited a 25.1% and 43.5% higher lap-shear strength and energy absorption, respectively, compared to those for the SPR joint.

    (4) The higher stiffness of the joint alleviated secondary bending under a cyclic tensile load, which delayed the fretting damage in the upper sheet and improved the load amplitudes by 18.4%and 14.5%for 105and 106fatigue lives,respectively,compared to those for the SPR joint.

    (5) The F-SPR process required a cycle time that was 0.8–2.9 s longer than that for the SPR process and approximately 0.3 g of rivet weight addition due to the rotational driving structures on the rivet head. Future studies for the F-SPR process may focus on improving the process efficiency and lightweight design of rivets.

    Acknowledgments

    The authors would like to acknowledge the financial support of the National Natural Science Foundation of China (52025058 and U1764251) and the National Key Research and Development Program of China (2016YFB0101606-8).

    Compliance with ethics guidelines

    Yunwu Ma, He Shan, Sizhe Niu, Yongbing Li, Zhongqin Lin, and Ninshu Ma declare that they have no conflict of interest or financial conflicts to disclose.

    成人国产av品久久久| 免费看日本二区| 水蜜桃什么品种好| 精品亚洲成a人片在线观看| 在线观看一区二区三区激情| 日韩欧美一区视频在线观看 | 免费大片18禁| av国产精品久久久久影院| 一级毛片我不卡| 简卡轻食公司| 高清在线视频一区二区三区| 亚洲无线观看免费| 午夜福利在线观看免费完整高清在| 菩萨蛮人人尽说江南好唐韦庄| 精品久久久久久电影网| 一区二区三区免费毛片| 欧美成人精品欧美一级黄| 新久久久久国产一级毛片| 国产伦在线观看视频一区| 成人亚洲欧美一区二区av| 亚洲成色77777| 2022亚洲国产成人精品| 九九久久精品国产亚洲av麻豆| 嫩草影院新地址| av不卡在线播放| 在线免费观看不下载黄p国产| 欧美3d第一页| 性高湖久久久久久久久免费观看| 国产成人精品无人区| 亚洲真实伦在线观看| 亚洲av成人精品一二三区| 国产亚洲欧美精品永久| 亚洲精品国产av成人精品| 亚洲欧美日韩另类电影网站| 女的被弄到高潮叫床怎么办| a级一级毛片免费在线观看| 精品酒店卫生间| 国产熟女欧美一区二区| 26uuu在线亚洲综合色| 99久久综合免费| 久久久久久久大尺度免费视频| 精品一品国产午夜福利视频| 插逼视频在线观看| 少妇人妻一区二区三区视频| 午夜久久久在线观看| 日日爽夜夜爽网站| 欧美丝袜亚洲另类| 两个人免费观看高清视频 | 国产亚洲欧美精品永久| 国产精品久久久久久av不卡| a级毛色黄片| 亚洲精品一区蜜桃| 看十八女毛片水多多多| 久久国产乱子免费精品| 午夜久久久在线观看| 好男人视频免费观看在线| 成年人午夜在线观看视频| 久热久热在线精品观看| 赤兔流量卡办理| 大香蕉久久网| 亚洲精品视频女| 国内揄拍国产精品人妻在线| 成人特级av手机在线观看| 午夜老司机福利剧场| 韩国高清视频一区二区三区| 国产欧美日韩精品一区二区| 成人午夜精彩视频在线观看| 天天操日日干夜夜撸| 欧美日韩精品成人综合77777| 在线观看三级黄色| 国精品久久久久久国模美| 熟女人妻精品中文字幕| 少妇精品久久久久久久| 夫妻性生交免费视频一级片| 日韩伦理黄色片| 国产精品欧美亚洲77777| 亚洲成人手机| 如何舔出高潮| 日韩成人伦理影院| 两个人的视频大全免费| 少妇人妻久久综合中文| 亚洲欧美日韩卡通动漫| 韩国高清视频一区二区三区| 午夜免费男女啪啪视频观看| 天天躁夜夜躁狠狠久久av| 亚洲国产av新网站| 99久久精品国产国产毛片| 在线亚洲精品国产二区图片欧美 | 一级毛片aaaaaa免费看小| 国产精品人妻久久久久久| 在线天堂最新版资源| 婷婷色综合大香蕉| 日韩成人av中文字幕在线观看| 国产乱来视频区| 国产淫语在线视频| 永久免费av网站大全| 免费播放大片免费观看视频在线观看| 久久久精品94久久精品| 国产 精品1| 91成人精品电影| 亚洲,欧美,日韩| 日本免费在线观看一区| 日韩制服骚丝袜av| 美女xxoo啪啪120秒动态图| 2021少妇久久久久久久久久久| 男人狂女人下面高潮的视频| 欧美老熟妇乱子伦牲交| a级毛片在线看网站| 精品久久久久久电影网| 91久久精品国产一区二区成人| 午夜91福利影院| 麻豆精品久久久久久蜜桃| 如何舔出高潮| 夫妻性生交免费视频一级片| 99热网站在线观看| 一区二区三区四区激情视频| 嘟嘟电影网在线观看| 久久这里有精品视频免费| 一级,二级,三级黄色视频| 各种免费的搞黄视频| 视频中文字幕在线观看| 老女人水多毛片| 亚洲中文av在线| 国产 一区精品| 中文精品一卡2卡3卡4更新| 乱系列少妇在线播放| 久久久久久久亚洲中文字幕| 国产免费福利视频在线观看| 亚洲精品国产成人久久av| 日韩亚洲欧美综合| 日韩视频在线欧美| 全区人妻精品视频| 国产日韩一区二区三区精品不卡 | 精品少妇内射三级| 99久久精品国产国产毛片| 成人综合一区亚洲| 男的添女的下面高潮视频| 狂野欧美激情性xxxx在线观看| 国产精品嫩草影院av在线观看| 欧美成人午夜免费资源| 国产成人精品久久久久久| www.色视频.com| 久久 成人 亚洲| 一级黄片播放器| 国产91av在线免费观看| 日韩,欧美,国产一区二区三区| 亚洲av成人精品一二三区| 免费观看性生交大片5| 久久99热6这里只有精品| 成年女人在线观看亚洲视频| 亚洲第一区二区三区不卡| 少妇人妻久久综合中文| 91精品伊人久久大香线蕉| 纯流量卡能插随身wifi吗| 欧美变态另类bdsm刘玥| 99视频精品全部免费 在线| 久久久国产一区二区| 一本大道久久a久久精品| 亚洲不卡免费看| 免费大片黄手机在线观看| 午夜福利在线观看免费完整高清在| 精品久久久久久久久亚洲| a级毛片免费高清观看在线播放| 嘟嘟电影网在线观看| 久久久久久久久久成人| 亚洲天堂av无毛| 成人影院久久| 婷婷色av中文字幕| 久久久久久久久久成人| 国产精品成人在线| 一本一本综合久久| 免费人成在线观看视频色| 亚洲欧美一区二区三区黑人 | 午夜老司机福利剧场| 中文字幕免费在线视频6| 欧美+日韩+精品| 亚洲精品久久久久久婷婷小说| 国产精品三级大全| 男人爽女人下面视频在线观看| 一级爰片在线观看| 高清午夜精品一区二区三区| 国产成人免费观看mmmm| 超碰97精品在线观看| 日韩在线高清观看一区二区三区| 亚洲精品日韩在线中文字幕| 日韩强制内射视频| 亚洲成人一二三区av| 亚洲,欧美,日韩| av免费观看日本| 久久久久久久精品精品| 国产精品久久久久久久久免| 女人久久www免费人成看片| 五月伊人婷婷丁香| videossex国产| 男人狂女人下面高潮的视频| kizo精华| 久久人人爽人人爽人人片va| 一级黄片播放器| 免费看不卡的av| 久久免费观看电影| 亚洲内射少妇av| 老司机影院成人| 十八禁高潮呻吟视频 | 久久99热这里只频精品6学生| 麻豆乱淫一区二区| 日韩,欧美,国产一区二区三区| 国产熟女午夜一区二区三区 | av一本久久久久| av女优亚洲男人天堂| 中文字幕久久专区| 亚洲一区二区三区欧美精品| 天美传媒精品一区二区| 久久久久久久久久久丰满| 五月开心婷婷网| 精品人妻偷拍中文字幕| 国精品久久久久久国模美| 亚洲丝袜综合中文字幕| 国产亚洲5aaaaa淫片| videossex国产| videos熟女内射| 日韩欧美一区视频在线观看 | 午夜激情福利司机影院| 国产有黄有色有爽视频| 夫妻午夜视频| 91精品国产九色| 欧美xxⅹ黑人| 成人漫画全彩无遮挡| 久久99热6这里只有精品| 欧美三级亚洲精品| 91久久精品国产一区二区三区| 国产乱来视频区| 你懂的网址亚洲精品在线观看| 亚州av有码| a 毛片基地| 亚洲中文av在线| 亚州av有码| 国产美女午夜福利| 人妻制服诱惑在线中文字幕| 18禁裸乳无遮挡动漫免费视频| 男人狂女人下面高潮的视频| 女人久久www免费人成看片| 亚洲av.av天堂| 成年人午夜在线观看视频| 国产精品国产av在线观看| 黄片无遮挡物在线观看| 亚洲情色 制服丝袜| 国产69精品久久久久777片| 99re6热这里在线精品视频| 久久99蜜桃精品久久| a级毛片免费高清观看在线播放| 97精品久久久久久久久久精品| av视频免费观看在线观看| 男女啪啪激烈高潮av片| 搡老乐熟女国产| 青春草国产在线视频| 不卡视频在线观看欧美| 最新中文字幕久久久久| 国产精品久久久久成人av| 国产色婷婷99| 亚洲美女黄色视频免费看| 观看美女的网站| 99热这里只有精品一区| 交换朋友夫妻互换小说| 3wmmmm亚洲av在线观看| 夜夜骑夜夜射夜夜干| 国产精品麻豆人妻色哟哟久久| 三级国产精品欧美在线观看| 人人澡人人妻人| 国产精品久久久久久精品古装| 亚洲在久久综合| 免费播放大片免费观看视频在线观看| 亚洲欧美中文字幕日韩二区| 精品一品国产午夜福利视频| 精品国产一区二区久久| 老司机影院成人| 两个人免费观看高清视频 | 男人和女人高潮做爰伦理| 成年女人在线观看亚洲视频| 五月伊人婷婷丁香| 国产精品久久久久成人av| 大香蕉久久网| 日韩中文字幕视频在线看片| 国产精品一区www在线观看| 97超碰精品成人国产| 精品久久久久久久久亚洲| 亚洲婷婷狠狠爱综合网| 精品亚洲成国产av| 国产永久视频网站| 国精品久久久久久国模美| 国产乱人偷精品视频| 永久免费av网站大全| 久久ye,这里只有精品| 久热久热在线精品观看| 免费观看av网站的网址| 一级毛片久久久久久久久女| 99热这里只有是精品在线观看| 亚洲第一区二区三区不卡| 国产亚洲最大av| 国产无遮挡羞羞视频在线观看| av有码第一页| 国产成人精品婷婷| 久热久热在线精品观看| 熟女电影av网| 日本爱情动作片www.在线观看| 久久精品国产亚洲av天美| 欧美日韩一区二区视频在线观看视频在线| 夫妻午夜视频| 纯流量卡能插随身wifi吗| 久久久欧美国产精品| 婷婷色综合大香蕉| 建设人人有责人人尽责人人享有的| 人妻制服诱惑在线中文字幕| 美女国产视频在线观看| 欧美日韩av久久| 亚洲,欧美,日韩| 成人国产麻豆网| 国产乱来视频区| 久久国产精品大桥未久av | 国产在线一区二区三区精| 成人美女网站在线观看视频| 中文字幕人妻丝袜制服| 丰满乱子伦码专区| 亚洲av综合色区一区| 成年人免费黄色播放视频 | 国产亚洲最大av| 青春草国产在线视频| 日本黄色日本黄色录像| 爱豆传媒免费全集在线观看| 观看免费一级毛片| 久久久午夜欧美精品| 国产av国产精品国产| 丝袜喷水一区| 免费人妻精品一区二区三区视频| 99九九在线精品视频 | 亚洲不卡免费看| 人妻夜夜爽99麻豆av| 男女国产视频网站| 亚洲国产成人一精品久久久| 三级国产精品欧美在线观看| 丰满迷人的少妇在线观看| 欧美成人午夜免费资源| 日韩av在线免费看完整版不卡| 亚洲四区av| 色5月婷婷丁香| av免费在线看不卡| 三级国产精品片| 国产男女超爽视频在线观看| 国产日韩一区二区三区精品不卡 | 少妇的逼好多水| 国产亚洲一区二区精品| 夜夜看夜夜爽夜夜摸| 久久ye,这里只有精品| 国产日韩欧美亚洲二区| av播播在线观看一区| 国模一区二区三区四区视频| kizo精华| 噜噜噜噜噜久久久久久91| 免费黄网站久久成人精品| 纵有疾风起免费观看全集完整版| 人人妻人人添人人爽欧美一区卜| 一个人免费看片子| 最新中文字幕久久久久| 少妇人妻精品综合一区二区| 男女啪啪激烈高潮av片| 日韩免费高清中文字幕av| 久久国产精品大桥未久av | 免费观看的影片在线观看| 成人午夜精彩视频在线观看| 久久久久人妻精品一区果冻| 少妇的逼水好多| 美女国产视频在线观看| 一级爰片在线观看| 亚洲欧美精品专区久久| 国产在视频线精品| 十八禁网站网址无遮挡 | 亚洲精华国产精华液的使用体验| 99热网站在线观看| 亚洲图色成人| 国产精品无大码| 国产69精品久久久久777片| 我的老师免费观看完整版| 99久国产av精品国产电影| 国产成人一区二区在线| 天美传媒精品一区二区| 人妻 亚洲 视频| 欧美另类一区| 99热这里只有是精品50| 人人妻人人澡人人看| 狠狠精品人妻久久久久久综合| 国内少妇人妻偷人精品xxx网站| 午夜免费鲁丝| 不卡视频在线观看欧美| 噜噜噜噜噜久久久久久91| 乱人伦中国视频| av播播在线观看一区| 亚洲欧美中文字幕日韩二区| 精品国产露脸久久av麻豆| 久久青草综合色| 人妻 亚洲 视频| 最新中文字幕久久久久| 麻豆精品久久久久久蜜桃| 街头女战士在线观看网站| 女性被躁到高潮视频| 黄色配什么色好看| av天堂久久9| 国产色婷婷99| 最近最新中文字幕免费大全7| 狂野欧美激情性bbbbbb| 国产亚洲5aaaaa淫片| 人妻少妇偷人精品九色| 你懂的网址亚洲精品在线观看| 高清不卡的av网站| a级片在线免费高清观看视频| 国产熟女午夜一区二区三区 | 天堂8中文在线网| 亚洲av综合色区一区| 精品酒店卫生间| 观看美女的网站| 少妇的逼水好多| 爱豆传媒免费全集在线观看| 99热这里只有精品一区| 亚洲熟女精品中文字幕| 麻豆精品久久久久久蜜桃| 两个人的视频大全免费| 欧美 亚洲 国产 日韩一| 精品国产露脸久久av麻豆| 黄色毛片三级朝国网站 | 日本vs欧美在线观看视频 | 国产精品国产三级专区第一集| 性色avwww在线观看| 精品少妇黑人巨大在线播放| 亚洲婷婷狠狠爱综合网| 成年人免费黄色播放视频 | 亚洲av不卡在线观看| 22中文网久久字幕| 日韩免费高清中文字幕av| 永久免费av网站大全| 一区二区三区免费毛片| 女性生殖器流出的白浆| av在线播放精品| 成人午夜精彩视频在线观看| 国产日韩一区二区三区精品不卡 | tube8黄色片| 最新的欧美精品一区二区| 女性被躁到高潮视频| 成人毛片a级毛片在线播放| 一级毛片我不卡| 精品少妇久久久久久888优播| 中文资源天堂在线| 免费观看性生交大片5| 国产白丝娇喘喷水9色精品| 久久久久久久精品精品| 国产男女超爽视频在线观看| 久久 成人 亚洲| 免费看不卡的av| av视频免费观看在线观看| 女人精品久久久久毛片| 女的被弄到高潮叫床怎么办| 女人精品久久久久毛片| 中文字幕人妻熟人妻熟丝袜美| 3wmmmm亚洲av在线观看| 如何舔出高潮| 国产精品成人在线| 97在线人人人人妻| 最黄视频免费看| 日本黄色片子视频| 久久99精品国语久久久| 男人爽女人下面视频在线观看| 欧美日本中文国产一区发布| 午夜福利视频精品| 人妻制服诱惑在线中文字幕| 视频中文字幕在线观看| 国产成人午夜福利电影在线观看| 精品久久久久久久久av| 精品久久久噜噜| 最新中文字幕久久久久| 国产色婷婷99| 亚洲国产欧美在线一区| 极品少妇高潮喷水抽搐| 日韩伦理黄色片| 国产精品蜜桃在线观看| 日韩一本色道免费dvd| 成年人午夜在线观看视频| 最近中文字幕2019免费版| 国产免费视频播放在线视频| 亚洲,欧美,日韩| 久久午夜综合久久蜜桃| 日韩精品免费视频一区二区三区 | 一区二区三区四区激情视频| 国产精品不卡视频一区二区| 中文精品一卡2卡3卡4更新| 一个人免费看片子| 美女国产视频在线观看| 亚洲精品乱码久久久v下载方式| 又大又黄又爽视频免费| 自线自在国产av| 久久99蜜桃精品久久| 国产91av在线免费观看| 免费久久久久久久精品成人欧美视频 | 美女国产视频在线观看| 少妇被粗大的猛进出69影院 | 九九久久精品国产亚洲av麻豆| 午夜影院在线不卡| 成人18禁高潮啪啪吃奶动态图 | 男的添女的下面高潮视频| 男人狂女人下面高潮的视频| 亚洲av男天堂| 在线观看人妻少妇| 日韩强制内射视频| 高清视频免费观看一区二区| 国产综合精华液| 黑丝袜美女国产一区| 丰满少妇做爰视频| 性高湖久久久久久久久免费观看| a 毛片基地| 天天躁夜夜躁狠狠久久av| 嘟嘟电影网在线观看| 精品国产乱码久久久久久小说| 美女视频免费永久观看网站| 日韩中文字幕视频在线看片| 大又大粗又爽又黄少妇毛片口| 国产亚洲午夜精品一区二区久久| 少妇被粗大的猛进出69影院 | av女优亚洲男人天堂| 国产精品福利在线免费观看| 久热久热在线精品观看| 日韩大片免费观看网站| 91成人精品电影| 免费高清在线观看视频在线观看| 久久国产亚洲av麻豆专区| 亚洲欧美日韩东京热| 日韩亚洲欧美综合| 亚洲美女黄色视频免费看| 国产精品久久久久久久久免| 亚洲国产欧美在线一区| 少妇精品久久久久久久| 欧美少妇被猛烈插入视频| 日韩在线高清观看一区二区三区| 啦啦啦中文免费视频观看日本| 精品酒店卫生间| 欧美少妇被猛烈插入视频| 成人免费观看视频高清| 亚洲高清免费不卡视频| 日韩av不卡免费在线播放| 亚洲人与动物交配视频| 亚洲精品aⅴ在线观看| 国内精品宾馆在线| 国产成人精品久久久久久| 久久国内精品自在自线图片| 99视频精品全部免费 在线| 亚洲欧美日韩另类电影网站| av在线观看视频网站免费| 亚洲精品乱码久久久v下载方式| 亚洲综合色惰| 中文字幕人妻熟人妻熟丝袜美| 国产精品一区二区在线不卡| 尾随美女入室| 夜夜骑夜夜射夜夜干| 人妻夜夜爽99麻豆av| 精品一区二区三区视频在线| 如日韩欧美国产精品一区二区三区 | 99热国产这里只有精品6| 九九爱精品视频在线观看| 日韩精品有码人妻一区| 日韩一区二区视频免费看| 搡老乐熟女国产| 国产伦在线观看视频一区| 综合色丁香网| 亚洲精品aⅴ在线观看| 免费黄色在线免费观看| 国产亚洲5aaaaa淫片| 色视频www国产| 精品一区二区免费观看| 日本欧美视频一区| 日韩av免费高清视频| kizo精华| 国产精品熟女久久久久浪| 高清黄色对白视频在线免费看 | 亚洲欧美成人精品一区二区| 国产视频首页在线观看| 80岁老熟妇乱子伦牲交| 午夜老司机福利剧场| 国产精品.久久久| 嫩草影院新地址| 岛国毛片在线播放| 毛片一级片免费看久久久久| 麻豆成人av视频| 精品久久久久久久久av| h视频一区二区三区| 搡老乐熟女国产| 成年人免费黄色播放视频 | 久久久精品94久久精品| 高清视频免费观看一区二区| 国产免费视频播放在线视频| 久久av网站| 午夜福利视频精品| 久久人妻熟女aⅴ| 在线 av 中文字幕| 少妇丰满av| 国产高清三级在线| 一级毛片电影观看| 国产午夜精品一二区理论片| 最近手机中文字幕大全| 国产成人精品无人区| 纯流量卡能插随身wifi吗| 最近最新中文字幕免费大全7| 亚洲在久久综合| 欧美日韩国产mv在线观看视频| 亚洲天堂av无毛| 人妻 亚洲 视频| 久久人人爽av亚洲精品天堂| 色94色欧美一区二区| 久久精品国产亚洲网站| 搡女人真爽免费视频火全软件| 乱人伦中国视频|