There are numerous riveting points on the large-sized aircraft panel, irregular row of riveting points on delta wing. It is essential to plan the riveting sequence reasonably to improve the efficiency and accuracy of ...There are numerous riveting points on the large-sized aircraft panel, irregular row of riveting points on delta wing. It is essential to plan the riveting sequence reasonably to improve the efficiency and accuracy of automatic drilling and riveting. Therefore, this article presents a new multi-objective optimization method based on ant colony optimization （ACO）. Multi-objective optimization model of automatic drilling and riveting sequence planning is built by expressing the efficiency and accuracy of riveting as functions of the points＇ coordinates. In order to search the sequences efficiently and improve the quality of the sequences, a new local pheromone updating rule is applied when the ants search sequences. Pareto dominance is incorporated into the proposed ACO to find out the non-dominated sequences. This method is tested on a hyperbolicity panel model of ARJ21 and the result shows its feasibility and superiority compared with particle swarm optimization （PSO） and genetic algorithm （GA）.展开更多
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...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.展开更多
With the increasing applications of novel materials and structures in new-generation aircraft,conventional joining techniques in aircraft component assembly are greatly challenged.To meet those challenges,the electrom...With the increasing applications of novel materials and structures in new-generation aircraft,conventional joining techniques in aircraft component assembly are greatly challenged.To meet those challenges,the electromagnetic riveting(EMR)technique was developed as an advanced joining tool,which exhibits obvious advantages in the assembly of new-generation aircraft.In this paper,the riveting principle of EMR was analyzed,and its development history and status were presented in detail.Then,equipment features of three typical EMR systems were given.Moreover,three important applications of EMR were covered,i.e.,composite structure riveting,titanium rivet and large-size aluminum rivet riveting,and interference fit bolt installation.Specially,a novel strengthening method for mechanical linking holes based on EMR was also presented,which can significantly improve the fatigue behaviors of mechanical joints.Finally,open questions in the EMR field were discussed,and some recommendations for future work were also made.This paper can be useful for optimizing the joint designs of aircraft components and improving the level of aircraft maintenance.展开更多
The riveting joint is one of the important joint methods to permanently fasten two thin-walled sheet-metal parts. It is most ba- sic to efficiently analyze and estimate the deformation of the riveting joint for the pe...The riveting joint is one of the important joint methods to permanently fasten two thin-walled sheet-metal parts. It is most ba- sic to efficiently analyze and estimate the deformation of the riveting joint for the performance, fatigue durability and damage of the riveting structure in the aircraft. This paper researches the riveting process mathematics modeling and simulating to more accurately analyze deformation of thin-walled sheet-metal parts. First, the mathematics and mechanics models for the elastic deformation, plastic deformation and springback of the rivet are built by mechanics theory. Second, on the basis of ABAQUS system, a finite element system, an instance made up of the rivet and two thin-walled sheet-metal parts of aluminum alloy is used to analyze and simulate the stress and deformation. What＇s more, a comparison is made between the results obtained by the mathematics and mechanics models and those by finite element method （FEM）. The models are proved true by the calculating and simulation results of the instance.展开更多
Self-piercing riveting(SPR)is a cold forming technique used to fasten together two or more sheets of materials with a rivet without the need to predrill a hole.The application of SPR in the automotive sector has becom...Self-piercing riveting(SPR)is a cold forming technique used to fasten together two or more sheets of materials with a rivet without the need to predrill a hole.The application of SPR in the automotive sector has become increasingly popular mainly due to the growing use of lightweight materials in transportation applications.However,SPR joining of these advanced light materials remains a challenge as these materials often lack a good combination of high strength and ductility to resist the large plastic deformation induced by the SPR process.In this paper,SPR joints of advanced materials and their corresponding failure mechanisms are discussed,aiming to provide the foundation for future improvement of SPR joint quality.This paper is divided into three major sections:1)joint failures focusing on joint defects originated from the SPR process and joint failure modes under different mechanical loading conditions,2)joint corrosion issues,and 3)joint optimisation via process parameters and advanced techniques.展开更多
To fulfill the demands for higher quality,efficiency and flexibility in aviation industry,a multi-functional end effector is designed to automate the drilling and riveting processes in assembling carbon fiber reinforc...To fulfill the demands for higher quality,efficiency and flexibility in aviation industry,a multi-functional end effector is designed to automate the drilling and riveting processes in assembling carbon fiber reinforced polymer(CFRP)and aluminum components for a robotic aircraft assembly system.To meet the specific functional requirements for blind rivet installation on CFRP and aluminum materials,additional modules are incorporated on the end effector aside of the basic processing modules for drilling.And all of these processing modules allow for a onestep-drilling-countersinking process,hole inspection,automatic rivet feed,rivet geometry check,sealant application,rivet insertion and installation.Besides,to guarantee the better quality of the hole drilled and joints riveted,several online detection and adjustment measures are applied to this end effector,including the reference detection and perpendicular calibration,which could effectively ensure the positioning precision and perpendicular accuracy as demanded.Finally,the test result shows that this end effector is capable of producing each hole to a positioning precision within ±0.5 mm,aperpendicular accuracy within 0.3°,a diameter tolerance of H8,and a countersink depth tolerance of±0.01 mm.Moreover,it could drill and rivet up to three joints per minute,with acceptable shearing and tensile strength.展开更多
The concave die design of self-pierce riveting(SPR) is of critical importance for product quality. The optimization of concave die parameters based on orthogonal test is proposed to explore the relationship between se...The concave die design of self-pierce riveting(SPR) is of critical importance for product quality. The optimization of concave die parameters based on orthogonal test is proposed to explore the relationship between self-pierce riveted joint quality and die parameters. There are nine independent die parameter factors in orthogonal test and each factor has 4 levels. In order to evaluate the interlock and neck thickness, we carry out numerical simulations by the software DEFORM-2D. Then, the primary and secondary factors that affect the joint quality have been found out by means of range analysis. Finally, an optimization scheme is brought forward to design concave die in SPR process, which indicates that the joint has higher quality than that of former orthogonal tests.This work can be extended by a detailed mechanical and fatigue analysis for the joint quality of SPR process.展开更多
A new testing methodology was developed to quantitively study galvanic corrosion of AZ31B and thermoset carbon-fiber–reinforced polymer spot-joined by a friction self-piercing riveting process.Pre-defined areas of AZ...A new testing methodology was developed to quantitively study galvanic corrosion of AZ31B and thermoset carbon-fiber–reinforced polymer spot-joined by a friction self-piercing riveting process.Pre-defined areas of AZ31B in the joint were exposed in 0.1 M NaCl solution over time.Massive galvanic corrosion of AZ31B was observed as exposure time increased.The measured volume loss was converted into corrosion current that was at least 48 times greater than the corrosion current of AZ31B without galvanic coupling.Ninety percent of the mechanical joint integrity was retained for corroded F-SPR joints to 200 h and then decreased because of the massive volume loss of AZ31B。展开更多
Carbon fiber reinforced plastic(CFRP)and aluminum stacks are widely used in aviation industry due to light weight and high performance.Millions of rivet holes need to be drilled on body materials,and more than 80%of f...Carbon fiber reinforced plastic(CFRP)and aluminum stacks are widely used in aviation industry due to light weight and high performance.Millions of rivet holes need to be drilled on body materials,and more than 80%of fatigue cracks occur at the connection holes,so the damage and residual stress of hole surface have crucial effect on the riveting fatigue life of CFRP/aluminum stacks and the flight performance.Recently,robotic rotary ultrasonic drilling(RRUD)technology is a promising method to machine the stacks.However,the hole surface strengthening mechanism in RRUD and the service performance of the riveting joint are not verified.Thus,in this paper,the hole surface strengthening mechanism of RRUD for CFRP/aluminum stacks is investigated,a theoretical residual stress model is established,and the fatigue life experiment of riveted joints is conducted.Firstly,analysis on residual stress in RRUD is carried out with consideration of strengthening force and cutting temperature.Residual stress model is established based on the calculation of elastic stress,plastic stress and stress release.Validation experiment results show that ultrasonic vibration changes residual stress from tensile stress to compressive stress.At the same time,comparative damage analysis of CFRP hole exit and hole surface in robotic conventional drilling(RCD)and RRUD is presented.Finally,fatigue strength experiments of riveted joints are conducted for performance verification.Experimental results indicate that fatigue life of single-hole riveted joints is increased by 68%with ultrasonic vibration,and four-hole riveted joint arranged according to aerospace design standards is increased by more than 86%.展开更多
Friction self-piercing riveting(F-SPR)process based on a pip die has been invented to solve the cracking problems in riveting high-strength and low-ductility light metals,such as magnesium alloys,cast aluminum,and 7 s...Friction self-piercing riveting(F-SPR)process based on a pip die has been invented to solve the cracking problems in riveting high-strength and low-ductility light metals,such as magnesium alloys,cast aluminum,and 7 series aluminum alloys.In this paper,in order to solve quality issues caused by the misalignment between rivet and pip-die in F-SPR,a flat-die based F-SPR process was proposed and employed to join 1.27 mm-thick AA6061-T6 to 3 mm-thick AZ31B.The results indicate that a 1.0 mm die distance is effective to avoid rivet upset and insufficient flaring.As the feed rate increases,the heat input in the whole process decreases,resulting in a larger riveting force,which in turn increases both the bottom thickness and interlock amount.Besides,solid-state bonding,including Al-Mg intermetallic compounds(IMCs),Al-Mg mechanical mixture,and Al-Fe atom interdiffusion was observed at the joint interfaces.The upper Al layer was softened,but the lower Mg layer was hardened,and both sheets exhibited a narrowed affected region with the increase of feed rate,while the rivet hardness shows no obvious change.Three fracture modes appeared accompanying the variations in lap-shear strength and energy absorption as the feed rate increased from 2 mm/s to 8 mm/s.Finally,the F-SPR process using a flat die was compared to those using a pip die and a flat bottom die to show the advantage of flat die on coping with the misalignment problem.展开更多
In order to eliminate the disadvantages of the keyhole in conventional friction stir spot welding joint and attain the highstrength lap joint of Al/Cu dissimilar metals,a novel welding technique,named as friction stir...In order to eliminate the disadvantages of the keyhole in conventional friction stir spot welding joint and attain the highstrength lap joint of Al/Cu dissimilar metals,a novel welding technique,named as friction stir spot riveting(FSSR),was proposed.A pinless tool and an extra filling stud were employed.The Al/Cu spot joints without keyhole defect were achieved by the FSSR.A Cu anchor-like structure was formed,which greatly increased the mechanical interlocking between the upper Al sheet and lower Cu sheet.The thin intermetallic compounds containing CuAl2 and CuAl at the Al/Cu interface strengthened the joining interface between the Al sheet and the Cu stud.Increasing rotating velocity increased frictional heat and plastic deformation and then eliminated the interfacial joining defects.The FSSR joint with the maximum tensile shear load of 3.50 kN was achieved at a rotating velocity of 1800 rpm and a dwell time of 20 s,whose fracture path passed through the softened region of upper Al sheet.In summary,the novel FSSR technique has the advantages of strong mechanical interlocking and metallurgical bonding between dissimilar materials,thereby attaining the high-strength spot joint.展开更多
The low-stiffness of aircraft skins may results in the differences between aircraft actual parts and their theoretical models,which will consequently affect the accuracy of automatic drilling and riveting in aircraft ...The low-stiffness of aircraft skins may results in the differences between aircraft actual parts and their theoretical models,which will consequently affect the accuracy of automatic drilling and riveting in aircraft assembly.In this paper,a novel approach of hole position correction using laser line scanner(LLS)is proposed to assign a single row of holes on the parts’surfaces.First,we adopt a space circle fitting method and the random sample consensus(RANSAC)to obtain the precise coordinates of center of the datum holes’coordinates.Second,LLS is calibrated by the laser tracker,and the relations between the LLS coordinate system and the tool coordinate system(TCS)can be calculated.Third,the kinematics model of the automatic riveting machine is established based on a two-point referencing strategy proposed in this paper.Thus,the positions of the holes to be drilled can be adjusted.Finally,the experimental results show that in TCS the measurement error of LLS is less than 0.1 mm,and the correction error of the hole position is less than 0.5 mm,which demonstrates the reliability of our method.展开更多
A new friction-based riveting technique, Rotating Hammer Riveting(RHR), is demonstrated to fully form AZ31 Mg rivet heads in a mere 0.23 s. Heat and pressure generated through severe plastic deformation during the pro...A new friction-based riveting technique, Rotating Hammer Riveting(RHR), is demonstrated to fully form AZ31 Mg rivet heads in a mere 0.23 s. Heat and pressure generated through severe plastic deformation during the process was sufficient to form the Mg rivet head without the need for a pre-heating operation. Due to preliminary twinning and followed by dynamic recrystallization, AZ31 Mg grains in the rivet head were refined during RHR, which enhance the formability of Mg rivets by triggering grain boundary sliding and reducing plastic anisotropy of Mg. In addition, RHR joints showed a metallurgical bond between the rivet head and top AZ31 Mg sheet, which eliminates a significant pathway for corrosion.展开更多
The rivet joints have been widely applied in aerospace and vehicle fields.During the joining process of the carbon fiber reinforced plastic(CFRP)laminates,the pre-tightening force of pulling-rivet was the key factor t...The rivet joints have been widely applied in aerospace and vehicle fields.During the joining process of the carbon fiber reinforced plastic(CFRP)laminates,the pre-tightening force of pulling-rivet was the key factor to ensure the connection performance.To predict the impact of clamping loads on stress and failure of laminates,the value of stress and damage evolution of the wall of a hole under the pre-tightening force were simulated by the finite element method.The results of the simulation showed that excessive clamping force led to the damage and failure of CFRP in the hole edge.Connection performance together with progressive failure process and failure modes of CFRP laminates with various pre-tightening forces were investigated.A kind of metal embedded parts embedded in the laminates was designed to reduce the damage by the simulation study.Simulation results showed that embedment reduced the failure and damage efficiently.The embedment reduced about 64%of the maximum stress.展开更多
The development and application of large Die⁃Casting Al Alloy(DCAA)parts and Thermo⁃Formed Steel Sheets(TFSS)in Body⁃in⁃White(BIW)have created higher demands for the joining technology of high⁃strength steel/Al dissim...The development and application of large Die⁃Casting Al Alloy(DCAA)parts and Thermo⁃Formed Steel Sheets(TFSS)in Body⁃in⁃White(BIW)have created higher demands for the joining technology of high⁃strength steel/Al dissimilar materials.As an emerging technology,Flush Self⁃Piercing Riveting(FSPR)is still in the experimental phase and undergoing small batch equipment verification.This paper focuses on the joining methods for DCAA and TFSS in BIW,investigating the joining mechanisms,technical features,and forming principles of FSPR for steel/Al dissimilar materials with two⁃layer or three⁃layer plate combinations.Considering the TL4225/C611/CR5 sheet combination as a subject,the forming mechanism of high⁃quality joints was studied,and a physical and mathematical model was established to depict the relationship between the filling amount of the arc⁃gap and die dimensions,as well as the extrusion amount.This model effectively illustrates the relationship between the filling amount of the flowing metal in the arc⁃gap and critical parameters,such as die dimensions and feeding amounts.By simplifying the process of selecting joining parameters,it significantly reduces both the time and experimental workload associated with parameter selection.This provides a technical foundation for the application of DAAA and TFSS parts in BIW,enabling the rapid choice of appropriate joining parameters to meet the requirements for obtaining high⁃quality joints.The model can be effectively utilized to investigate the relationships between key parameters,including arc⁃gap radius,plate thickness,rivet arc radius,nail head radius,groove width,and feeding amount,while keeping other parameters constant.This approach provides a theoretical foundation for the design of Friction Stir Processing(FSP)joints and aids in the selection of optimal parameters.展开更多
The multi-material assembled light alloy wheel presents an effective lightweight solution for new energy vehicles,but its riveting connection remains a problem.To address this problem,this paper proposed the explicit ...The multi-material assembled light alloy wheel presents an effective lightweight solution for new energy vehicles,but its riveting connection remains a problem.To address this problem,this paper proposed the explicit riveting-implicit springback-implicit fatigue/explicit impact sequence coupling simulation analysis method,analyzed the fatigue and impact performance of the punching riveting connected magnesium/aluminum alloy(Mg/Al)assembled wheel,and constructed some major evaluation indicators.The accuracy of the proposed simulation method was verified by conducting physical experiments of single and cross lap joints.The punching riveting process parameters of the assembled wheel joints were defined as design variables,and the fatigue and impact performance of the assembled wheel was defined as the optimization objective.The connection-performance integration multi-objective optimization design of the assembled wheel considering riveting residual stress was designed via Taguchi experiment,grey relational analysis,analytic hierarchy process,principal component analysis,and entropy weighting methods.The optimization results of the three weighting methods were compared,and the optimal combination of design variables was determined.The fatigue and impact performance of the Mg/Al assembled wheel were effectively improved after optimization.展开更多
Dispersing metals from nanoparticles to clusters is often achieved using ligand protection methods,which exhibit unique properties such as suppressing structure-sensitive side reactions.However,this method is limited ...Dispersing metals from nanoparticles to clusters is often achieved using ligand protection methods,which exhibit unique properties such as suppressing structure-sensitive side reactions.However,this method is limited by the use of different metal precursor salts corresponding to different ligands.An alternative approach,the ion exchange(IE)method,can overcome this limitation to some extent.Nevertheless,there is still an urgent need to address the stabilization of metals(especially precious metals)by using IE method.Here,we reported a Pt cluster catalyst prepared mainly by anchoring Pt atoms via O located near the framework Zn in zincosilicate zeolites and riveted by zeolite surface rings after reduction(reduced Pt/Zn-3-IE).The catalyst can achieve an initial propane conversion of 26%in a pure propane atmosphere at 550℃and shows little deactivation even after 7.5 d of operation.Moreover,the alteration of catalyst by the introduction of framework Zn was also highlighted and interpreted.展开更多
Multi-layer riveted structures are widely applied to aircraft.During the service,cracks may appear within these structures due to stress concentration of the riveted holes.The guided wave monitoring has been proved to...Multi-layer riveted structures are widely applied to aircraft.During the service,cracks may appear within these structures due to stress concentration of the riveted holes.The guided wave monitoring has been proved to be an effective tool to deal with this problem.However,there is a lack of understanding of the wave propagation process across such kinds of structures.This study proposes a piezoelectric guided wave simulation method to reveal the propagation of guided waves in multi-layer riveted structures.Effects of pretension force,friction coefficient,and cracks that might influence wave characteristics are studied.The guided wave simulation data is compared with the experimental results and the results verify the simulation model.Then the guided wave propagation in a more complex long-beam butt joint structure is further simulated.展开更多
Given their numerous functional and architectural benefits,such as improved bearing capacity and increased resistance to elastic instability modes,cold-formed steel(CFS)built-up sections have become increasingly devel...Given their numerous functional and architectural benefits,such as improved bearing capacity and increased resistance to elastic instability modes,cold-formed steel(CFS)built-up sections have become increasingly developed and used in recent years,particularly in the construction industry.This paper presents an analytical and numerical study of assembled CFS two single channel-shaped columns with different slenderness and configurations(backto-back,face-to-face,and box).These columns were joined by double-row rivets for the back-to-back and box configurations,whereas they were welded together for the face-to-face design.The built-up columns were filled with ordinary concrete of good strength.Finite element models were applied,using ABAQUS software,to assess mechanical performance and study the influence of assembly techniques on the behavior of cold-formed columns under axial compression.Analytical approaches based on Eurocode 3 and Eurocode 4 recommendations for un-filled and concrete-filled columns respectively were followed for the numerical analysis,and concrete confinement effects were also considered per American Concrete Institute(ACI)standards for face-to-face and box configurations.The obtained results indicated a good correlation between the numerical results and the proposed analytical methodology which did not exceed 8%.The failure modes showed that the columns failed due to instabilities such as local and global buckling.展开更多
Self-piercing riveting(SPR)has been widely used in automobile industry,and the strength prediction of SPR joints always attracts the attention of researchers.In this work,a prediction method of the cross-tension stren...Self-piercing riveting(SPR)has been widely used in automobile industry,and the strength prediction of SPR joints always attracts the attention of researchers.In this work,a prediction method of the cross-tension strength of SPR joints was proposed on the basis of finite element(FE)simulation and extreme gradient boosting decision tree(XGBoost)algorithm.An FE model of SPR process was established to simulate the plastic deformations of rivet and substrate materials and verified in terms of cross-sectional dimensions of SPR joints.The residual mechanical field from SPR process simulation was imported into a 2D FE model for the cross-tension testing simulation of SPR joints,and cross-tension strengths from FE simulation show a good consistence with the experiment result.Based on the verified FE model,the mechanical properties and thickness of substrate materials were varied and then used for FE simulation to obtain cross-tension strengths of a number of SPR joints,which were used to train the regression model based on the XGBoost algorithm in order to achieve prediction for cross-tension strength of SPR joints.Results show that the cross-tension strengths of SPR steel/aluminum joints could be successfully predicted by the XGBoost regression model with a respective error less than 7.6%compared to experimental values.展开更多
基金National Natural Science Foundation of China (50805119)Aeronautical Science Foundation of China (2009ZE53)
文摘There are numerous riveting points on the large-sized aircraft panel, irregular row of riveting points on delta wing. It is essential to plan the riveting sequence reasonably to improve the efficiency and accuracy of automatic drilling and riveting. Therefore, this article presents a new multi-objective optimization method based on ant colony optimization （ACO）. Multi-objective optimization model of automatic drilling and riveting sequence planning is built by expressing the efficiency and accuracy of riveting as functions of the points＇ coordinates. In order to search the sequences efficiently and improve the quality of the sequences, a new local pheromone updating rule is applied when the ants search sequences. Pareto dominance is incorporated into the proposed ACO to find out the non-dominated sequences. This method is tested on a hyperbolicity panel model of ARJ21 and the result shows its feasibility and superiority compared with particle swarm optimization （PSO） and genetic algorithm （GA）.
基金The authors would like to acknowledge the financial support of the National Natural Science Foundation of China(52025058 and U1764251)the National Key Research and Development Program of China(2016YFB0101606-8).
文摘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.
基金funded by the Major National Research Project of Numerical Control Machine and Basic Manufacturing Equipment of China(No.2016ZX04002004-008).
文摘With the increasing applications of novel materials and structures in new-generation aircraft,conventional joining techniques in aircraft component assembly are greatly challenged.To meet those challenges,the electromagnetic riveting(EMR)technique was developed as an advanced joining tool,which exhibits obvious advantages in the assembly of new-generation aircraft.In this paper,the riveting principle of EMR was analyzed,and its development history and status were presented in detail.Then,equipment features of three typical EMR systems were given.Moreover,three important applications of EMR were covered,i.e.,composite structure riveting,titanium rivet and large-size aluminum rivet riveting,and interference fit bolt installation.Specially,a novel strengthening method for mechanical linking holes based on EMR was also presented,which can significantly improve the fatigue behaviors of mechanical joints.Finally,open questions in the EMR field were discussed,and some recommendations for future work were also made.This paper can be useful for optimizing the joint designs of aircraft components and improving the level of aircraft maintenance.
基金National Natural Science Foundation of China （50805119） Aeronautical Science Foundation in China （2010ZE53049） Fund of National Engineering and Research Center for Commercial Aircraft Manufacturing （SAMC11 -JS-07-200）
文摘The riveting joint is one of the important joint methods to permanently fasten two thin-walled sheet-metal parts. It is most ba- sic to efficiently analyze and estimate the deformation of the riveting joint for the performance, fatigue durability and damage of the riveting structure in the aircraft. This paper researches the riveting process mathematics modeling and simulating to more accurately analyze deformation of thin-walled sheet-metal parts. First, the mathematics and mechanics models for the elastic deformation, plastic deformation and springback of the rivet are built by mechanics theory. Second, on the basis of ABAQUS system, a finite element system, an instance made up of the rivet and two thin-walled sheet-metal parts of aluminum alloy is used to analyze and simulate the stress and deformation. What＇s more, a comparison is made between the results obtained by the mathematics and mechanics models and those by finite element method （FEM）. The models are proved true by the calculating and simulation results of the instance.
文摘Self-piercing riveting(SPR)is a cold forming technique used to fasten together two or more sheets of materials with a rivet without the need to predrill a hole.The application of SPR in the automotive sector has become increasingly popular mainly due to the growing use of lightweight materials in transportation applications.However,SPR joining of these advanced light materials remains a challenge as these materials often lack a good combination of high strength and ductility to resist the large plastic deformation induced by the SPR process.In this paper,SPR joints of advanced materials and their corresponding failure mechanisms are discussed,aiming to provide the foundation for future improvement of SPR joint quality.This paper is divided into three major sections:1)joint failures focusing on joint defects originated from the SPR process and joint failure modes under different mechanical loading conditions,2)joint corrosion issues,and 3)joint optimisation via process parameters and advanced techniques.
基金supported by the National Natural Science Foundations of China(Nos.5157051626,51475225)
文摘To fulfill the demands for higher quality,efficiency and flexibility in aviation industry,a multi-functional end effector is designed to automate the drilling and riveting processes in assembling carbon fiber reinforced polymer(CFRP)and aluminum components for a robotic aircraft assembly system.To meet the specific functional requirements for blind rivet installation on CFRP and aluminum materials,additional modules are incorporated on the end effector aside of the basic processing modules for drilling.And all of these processing modules allow for a onestep-drilling-countersinking process,hole inspection,automatic rivet feed,rivet geometry check,sealant application,rivet insertion and installation.Besides,to guarantee the better quality of the hole drilled and joints riveted,several online detection and adjustment measures are applied to this end effector,including the reference detection and perpendicular calibration,which could effectively ensure the positioning precision and perpendicular accuracy as demanded.Finally,the test result shows that this end effector is capable of producing each hole to a positioning precision within ±0.5 mm,aperpendicular accuracy within 0.3°,a diameter tolerance of H8,and a countersink depth tolerance of±0.01 mm.Moreover,it could drill and rivet up to three joints per minute,with acceptable shearing and tensile strength.
基金the National Natural Science Foundation of China(No.51375282)the China Postdoctoral Science Foundation(No.2012T50621)the Open Fund of Shanghai Key Laboratory of Digital Manufacture for Thin-walled Structures(No.2011003)
文摘The concave die design of self-pierce riveting(SPR) is of critical importance for product quality. The optimization of concave die parameters based on orthogonal test is proposed to explore the relationship between self-pierce riveted joint quality and die parameters. There are nine independent die parameter factors in orthogonal test and each factor has 4 levels. In order to evaluate the interlock and neck thickness, we carry out numerical simulations by the software DEFORM-2D. Then, the primary and secondary factors that affect the joint quality have been found out by means of range analysis. Finally, an optimization scheme is brought forward to design concave die in SPR process, which indicates that the joint has higher quality than that of former orthogonal tests.This work can be extended by a detailed mechanical and fatigue analysis for the joint quality of SPR process.
基金financially sponsored by the US Department Energy Vehicle Technologies Office, as part of the Joining Core Programmanaged by UT-Battelle LLC for the US Department of Energy under Contract DE-AC05-00OR22725。
文摘A new testing methodology was developed to quantitively study galvanic corrosion of AZ31B and thermoset carbon-fiber–reinforced polymer spot-joined by a friction self-piercing riveting process.Pre-defined areas of AZ31B in the joint were exposed in 0.1 M NaCl solution over time.Massive galvanic corrosion of AZ31B was observed as exposure time increased.The measured volume loss was converted into corrosion current that was at least 48 times greater than the corrosion current of AZ31B without galvanic coupling.Ninety percent of the mechanical joint integrity was retained for corroded F-SPR joints to 200 h and then decreased because of the massive volume loss of AZ31B。
基金the the Project on the Technological Leading Talent Teams Led by Frontiers Science Center for Complex Equipment System Dynamics(No.FSCCESD220401)the Jiangsu Funding Program for Excellent Postdoctoral Talent(No.2022ZB264).
文摘Carbon fiber reinforced plastic(CFRP)and aluminum stacks are widely used in aviation industry due to light weight and high performance.Millions of rivet holes need to be drilled on body materials,and more than 80%of fatigue cracks occur at the connection holes,so the damage and residual stress of hole surface have crucial effect on the riveting fatigue life of CFRP/aluminum stacks and the flight performance.Recently,robotic rotary ultrasonic drilling(RRUD)technology is a promising method to machine the stacks.However,the hole surface strengthening mechanism in RRUD and the service performance of the riveting joint are not verified.Thus,in this paper,the hole surface strengthening mechanism of RRUD for CFRP/aluminum stacks is investigated,a theoretical residual stress model is established,and the fatigue life experiment of riveted joints is conducted.Firstly,analysis on residual stress in RRUD is carried out with consideration of strengthening force and cutting temperature.Residual stress model is established based on the calculation of elastic stress,plastic stress and stress release.Validation experiment results show that ultrasonic vibration changes residual stress from tensile stress to compressive stress.At the same time,comparative damage analysis of CFRP hole exit and hole surface in robotic conventional drilling(RCD)and RRUD is presented.Finally,fatigue strength experiments of riveted joints are conducted for performance verification.Experimental results indicate that fatigue life of single-hole riveted joints is increased by 68%with ultrasonic vibration,and four-hole riveted joint arranged according to aerospace design standards is increased by more than 86%.
基金financial support of the National Natural Science Foundation of China(Grant Nos.52025058 and U1764251)。
文摘Friction self-piercing riveting(F-SPR)process based on a pip die has been invented to solve the cracking problems in riveting high-strength and low-ductility light metals,such as magnesium alloys,cast aluminum,and 7 series aluminum alloys.In this paper,in order to solve quality issues caused by the misalignment between rivet and pip-die in F-SPR,a flat-die based F-SPR process was proposed and employed to join 1.27 mm-thick AA6061-T6 to 3 mm-thick AZ31B.The results indicate that a 1.0 mm die distance is effective to avoid rivet upset and insufficient flaring.As the feed rate increases,the heat input in the whole process decreases,resulting in a larger riveting force,which in turn increases both the bottom thickness and interlock amount.Besides,solid-state bonding,including Al-Mg intermetallic compounds(IMCs),Al-Mg mechanical mixture,and Al-Fe atom interdiffusion was observed at the joint interfaces.The upper Al layer was softened,but the lower Mg layer was hardened,and both sheets exhibited a narrowed affected region with the increase of feed rate,while the rivet hardness shows no obvious change.Three fracture modes appeared accompanying the variations in lap-shear strength and energy absorption as the feed rate increased from 2 mm/s to 8 mm/s.Finally,the F-SPR process using a flat die was compared to those using a pip die and a flat bottom die to show the advantage of flat die on coping with the misalignment problem.
基金financially supported by the National Natural Science Foundation of China (Nos.51705339 and 51905355)。
文摘In order to eliminate the disadvantages of the keyhole in conventional friction stir spot welding joint and attain the highstrength lap joint of Al/Cu dissimilar metals,a novel welding technique,named as friction stir spot riveting(FSSR),was proposed.A pinless tool and an extra filling stud were employed.The Al/Cu spot joints without keyhole defect were achieved by the FSSR.A Cu anchor-like structure was formed,which greatly increased the mechanical interlocking between the upper Al sheet and lower Cu sheet.The thin intermetallic compounds containing CuAl2 and CuAl at the Al/Cu interface strengthened the joining interface between the Al sheet and the Cu stud.Increasing rotating velocity increased frictional heat and plastic deformation and then eliminated the interfacial joining defects.The FSSR joint with the maximum tensile shear load of 3.50 kN was achieved at a rotating velocity of 1800 rpm and a dwell time of 20 s,whose fracture path passed through the softened region of upper Al sheet.In summary,the novel FSSR technique has the advantages of strong mechanical interlocking and metallurgical bonding between dissimilar materials,thereby attaining the high-strength spot joint.
基金supported by the National Natural Science Foundation of China (No.51875287)the National Defense Basic Scientific Research Program of China (No.JCKY2018605C010)the National Key Research and Development Program of China (No.2018YFB1306800)
文摘The low-stiffness of aircraft skins may results in the differences between aircraft actual parts and their theoretical models,which will consequently affect the accuracy of automatic drilling and riveting in aircraft assembly.In this paper,a novel approach of hole position correction using laser line scanner(LLS)is proposed to assign a single row of holes on the parts’surfaces.First,we adopt a space circle fitting method and the random sample consensus(RANSAC)to obtain the precise coordinates of center of the datum holes’coordinates.Second,LLS is calibrated by the laser tracker,and the relations between the LLS coordinate system and the tool coordinate system(TCS)can be calculated.Third,the kinematics model of the automatic riveting machine is established based on a two-point referencing strategy proposed in this paper.Thus,the positions of the holes to be drilled can be adjusted.Finally,the experimental results show that in TCS the measurement error of LLS is less than 0.1 mm,and the correction error of the hole position is less than 0.5 mm,which demonstrates the reliability of our method.
基金the support of the U.S.Department of Energy Vehicle Technologies Office(DOE/VTO)Joining Core Program。
文摘A new friction-based riveting technique, Rotating Hammer Riveting(RHR), is demonstrated to fully form AZ31 Mg rivet heads in a mere 0.23 s. Heat and pressure generated through severe plastic deformation during the process was sufficient to form the Mg rivet head without the need for a pre-heating operation. Due to preliminary twinning and followed by dynamic recrystallization, AZ31 Mg grains in the rivet head were refined during RHR, which enhance the formability of Mg rivets by triggering grain boundary sliding and reducing plastic anisotropy of Mg. In addition, RHR joints showed a metallurgical bond between the rivet head and top AZ31 Mg sheet, which eliminates a significant pathway for corrosion.
文摘The rivet joints have been widely applied in aerospace and vehicle fields.During the joining process of the carbon fiber reinforced plastic(CFRP)laminates,the pre-tightening force of pulling-rivet was the key factor to ensure the connection performance.To predict the impact of clamping loads on stress and failure of laminates,the value of stress and damage evolution of the wall of a hole under the pre-tightening force were simulated by the finite element method.The results of the simulation showed that excessive clamping force led to the damage and failure of CFRP in the hole edge.Connection performance together with progressive failure process and failure modes of CFRP laminates with various pre-tightening forces were investigated.A kind of metal embedded parts embedded in the laminates was designed to reduce the damage by the simulation study.Simulation results showed that embedment reduced the failure and damage efficiently.The embedment reduced about 64%of the maximum stress.
文摘The development and application of large Die⁃Casting Al Alloy(DCAA)parts and Thermo⁃Formed Steel Sheets(TFSS)in Body⁃in⁃White(BIW)have created higher demands for the joining technology of high⁃strength steel/Al dissimilar materials.As an emerging technology,Flush Self⁃Piercing Riveting(FSPR)is still in the experimental phase and undergoing small batch equipment verification.This paper focuses on the joining methods for DCAA and TFSS in BIW,investigating the joining mechanisms,technical features,and forming principles of FSPR for steel/Al dissimilar materials with two⁃layer or three⁃layer plate combinations.Considering the TL4225/C611/CR5 sheet combination as a subject,the forming mechanism of high⁃quality joints was studied,and a physical and mathematical model was established to depict the relationship between the filling amount of the arc⁃gap and die dimensions,as well as the extrusion amount.This model effectively illustrates the relationship between the filling amount of the flowing metal in the arc⁃gap and critical parameters,such as die dimensions and feeding amounts.By simplifying the process of selecting joining parameters,it significantly reduces both the time and experimental workload associated with parameter selection.This provides a technical foundation for the application of DAAA and TFSS parts in BIW,enabling the rapid choice of appropriate joining parameters to meet the requirements for obtaining high⁃quality joints.The model can be effectively utilized to investigate the relationships between key parameters,including arc⁃gap radius,plate thickness,rivet arc radius,nail head radius,groove width,and feeding amount,while keeping other parameters constant.This approach provides a theoretical foundation for the design of Friction Stir Processing(FSP)joints and aids in the selection of optimal parameters.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.51975244 and 51475201).The authors would like to express their appreciations for the fund supports.
文摘The multi-material assembled light alloy wheel presents an effective lightweight solution for new energy vehicles,but its riveting connection remains a problem.To address this problem,this paper proposed the explicit riveting-implicit springback-implicit fatigue/explicit impact sequence coupling simulation analysis method,analyzed the fatigue and impact performance of the punching riveting connected magnesium/aluminum alloy(Mg/Al)assembled wheel,and constructed some major evaluation indicators.The accuracy of the proposed simulation method was verified by conducting physical experiments of single and cross lap joints.The punching riveting process parameters of the assembled wheel joints were defined as design variables,and the fatigue and impact performance of the assembled wheel was defined as the optimization objective.The connection-performance integration multi-objective optimization design of the assembled wheel considering riveting residual stress was designed via Taguchi experiment,grey relational analysis,analytic hierarchy process,principal component analysis,and entropy weighting methods.The optimization results of the three weighting methods were compared,and the optimal combination of design variables was determined.The fatigue and impact performance of the Mg/Al assembled wheel were effectively improved after optimization.
文摘Dispersing metals from nanoparticles to clusters is often achieved using ligand protection methods,which exhibit unique properties such as suppressing structure-sensitive side reactions.However,this method is limited by the use of different metal precursor salts corresponding to different ligands.An alternative approach,the ion exchange(IE)method,can overcome this limitation to some extent.Nevertheless,there is still an urgent need to address the stabilization of metals(especially precious metals)by using IE method.Here,we reported a Pt cluster catalyst prepared mainly by anchoring Pt atoms via O located near the framework Zn in zincosilicate zeolites and riveted by zeolite surface rings after reduction(reduced Pt/Zn-3-IE).The catalyst can achieve an initial propane conversion of 26%in a pure propane atmosphere at 550℃and shows little deactivation even after 7.5 d of operation.Moreover,the alteration of catalyst by the introduction of framework Zn was also highlighted and interpreted.
文摘Multi-layer riveted structures are widely applied to aircraft.During the service,cracks may appear within these structures due to stress concentration of the riveted holes.The guided wave monitoring has been proved to be an effective tool to deal with this problem.However,there is a lack of understanding of the wave propagation process across such kinds of structures.This study proposes a piezoelectric guided wave simulation method to reveal the propagation of guided waves in multi-layer riveted structures.Effects of pretension force,friction coefficient,and cracks that might influence wave characteristics are studied.The guided wave simulation data is compared with the experimental results and the results verify the simulation model.Then the guided wave propagation in a more complex long-beam butt joint structure is further simulated.
文摘Given their numerous functional and architectural benefits,such as improved bearing capacity and increased resistance to elastic instability modes,cold-formed steel(CFS)built-up sections have become increasingly developed and used in recent years,particularly in the construction industry.This paper presents an analytical and numerical study of assembled CFS two single channel-shaped columns with different slenderness and configurations(backto-back,face-to-face,and box).These columns were joined by double-row rivets for the back-to-back and box configurations,whereas they were welded together for the face-to-face design.The built-up columns were filled with ordinary concrete of good strength.Finite element models were applied,using ABAQUS software,to assess mechanical performance and study the influence of assembly techniques on the behavior of cold-formed columns under axial compression.Analytical approaches based on Eurocode 3 and Eurocode 4 recommendations for un-filled and concrete-filled columns respectively were followed for the numerical analysis,and concrete confinement effects were also considered per American Concrete Institute(ACI)standards for face-to-face and box configurations.The obtained results indicated a good correlation between the numerical results and the proposed analytical methodology which did not exceed 8%.The failure modes showed that the columns failed due to instabilities such as local and global buckling.
基金Supported by National Natural Science Foundation of China(Grant No.51805375).
文摘Self-piercing riveting(SPR)has been widely used in automobile industry,and the strength prediction of SPR joints always attracts the attention of researchers.In this work,a prediction method of the cross-tension strength of SPR joints was proposed on the basis of finite element(FE)simulation and extreme gradient boosting decision tree(XGBoost)algorithm.An FE model of SPR process was established to simulate the plastic deformations of rivet and substrate materials and verified in terms of cross-sectional dimensions of SPR joints.The residual mechanical field from SPR process simulation was imported into a 2D FE model for the cross-tension testing simulation of SPR joints,and cross-tension strengths from FE simulation show a good consistence with the experiment result.Based on the verified FE model,the mechanical properties and thickness of substrate materials were varied and then used for FE simulation to obtain cross-tension strengths of a number of SPR joints,which were used to train the regression model based on the XGBoost algorithm in order to achieve prediction for cross-tension strength of SPR joints.Results show that the cross-tension strengths of SPR steel/aluminum joints could be successfully predicted by the XGBoost regression model with a respective error less than 7.6%compared to experimental values.
