Research On The Joint Static Strength Of Rotated Clinching Of Metallic Sheets

In recent years,with the development concept of green environmental protection and energy saving has been deeply rooted in the hearts of the people,the lightweight design has become an important issue in the process of product design and manufacturing.The use of lightweight materials is the most direct method,and the joining process of various lightweight materials is particularly important.For this reason,some new joining processes have been developed.Rotated clinching technology is a new type of plate joining process obtained by improving the traditional clinching technology,and the joining strength of this technology deserves the most attention.Therefore,it is of great significance to study the static strength of its j oints.In this paper,the 2.0 mm thick Al1060 plate is taken as the research object,and the static strength(shear strength and tensile strength)of the rotated clinching joint is studied by numerical simulation,experimental research and theoretical analysis.The effects of mould and process parameters onjoint section parameters and shear strength were studied by finite element simulation.Based on the simulation results,the BBD method in response surface analysis is used to study the weight of each parameter and the interaction between the two parameters on the static strength,and the best forming parameters of static strength are obtained.The static strength of the joint is verified by experiment.Finally,the mechanical model of static strength is established by using the method of theoretical analysis,the calculation formulas of static strength under different conditions are obtained,and the calculation results are compared with the test results.The conclusions of this paper are as follows:(1)The simulation results show that,the main factors affecting the static strength of the joint are the depth of die,the rotation angle of the punch,the inner and outer corner of punch.The shear strength increases with the increase of rotation angle(the decrease of bottom thickness),decreases with the increase of the depth of die,and changes little with the increase of inner and outer corner of punch.(2)The results of response surface analysis show that,the weight of the influence of the depth of die,the inner corner of punch and the outer corner of punch on the joint shear strength is 0.79,0.2 and 0.01 respectively.When the depth of die is 2.26 mm,the inner corner of punch is 0.3 mm,and the outer corner of punch is 1.36 mm,the maximum static strength of the formed joint is 1239.73N.(3)The test results show that,When the depth of die is 2.2 mm,the shear strength of the joint increases with the decrease of the bottom thickness,but tends to be flat in the later stage.When the depth of die is 2.3 mm and 2.4 mm,the shear strength of the joint increases first and then decreases with the decrease of the bottom thickness.Under the three die depths,the peel strength of the joint decreases with the increase of the bottom thickness.When the depth of die is 2.3 mm,the static strength of the joint is better,and the optimal bottom thickness range of shear strength and peel strength is 20%-30%and 15%-25%of the total thickness of the sheet respectively,the experimental and simulation results are basically consistent.(4)The theoretical calculation formula of joint shear strength is F1=σ·A=σ·[BL(L-2Tn1)(B-2T2)+BH],the theoretical calculation formula of joint peel strength is F2=σL·π(R2-RP2)·η.The shear strength mainly depends on the area of the fracture surface,and the larger the fracture area,the higher the shear strength of the joint.The peel strength is mainly determined by the drawing stress of the material,the interlock value of the joint and the neck thickness,and its interlock value has a great influence.Through the above research,it can be seen that the peel strength of rotated clinching joint can be effectively improved by reducing the bottom thickness(increasing the rotation angle).