Quality Prediction Of Self-piercing Riveted Joints And Static Study Under Acid Corrosion

Self-piercing riveting technology is widely used in the field of new-type lightweight body manufacturing.It is convenient and more accurate and faster to control and accept the quality of self-piercing riveting joints.In this paper,10 sets of self-piercing riveting tests of aluminum alloys with different thicknesses and different materials were carried out.The forming mechanism and influencing factors of the self-piercing riveting joints were analyzed.Through the derivation of mathematical geometric relationship and the combination of actual process parameters,the quality and static strength of self-piercing riveted joints are studied.The car body will be corroded in different environments during the actual use of the car.In order to facilitate a more intuitive and detailed observation of the corrosion effect of the self-piercing riveting test piece with different corrosion durations.In this paper,the self-piercing riveting test piece of aluminum-aluminum homogenous metal and the self-piercing riveting test piece of steel-aluminum dissimilar metal are placed in 0.02mol/L Na HSO₃ solution through the wet and dry immersion corrosion test in an acid environment.After the self-piercing riveting test piece,the analysis methods of corrosion dynamics,corrosion rate,static tensile test and fracture energy spectrum test were used to study the corrosion behavior and mechanical properties of the self-piercing riveting test piece after corrosion,and passed the electrochemical test.Simulation and simulation method to observe the corrosion process of self-piercing riveting specimens.The load-stroke curve generated during the riveting of the self-piercing riveting test piece is divided into four parts.It is found that the thickness of the plate,the depth of the lower mold cavity,the hardness of the plate and the hardness of the rivet are the main factors affecting the first part;the thickness of the upper plate is the influence The main factor of the second part,and the thickness value is approximately equal to the span value of the abscissa;the inner cavity volume of the lower mold,the rivet hardness and the hardness of the plate material are the main factors affecting the third part;the hardness of the rivet,the hardness of the plate material,the total plate Thickness and cavity volume are the main factors affecting the fourth part,and the larger the span value of the abscissa,the better the self-locking structure of the self-piercing riveting joints and the greater the static strength.And determine that the expansion of the rivet occurs at the end of the third part.By constructing a mathematical model,through the derivation of the mathematical geometric relationship and combining with the actual process parameters,the prediction formula of the nail foot opening of the self-piercing riveting joints and the prediction formula of the static strength are obtained.The maximum error values of the 10 groups of test pieces are10.42%and 5.28%,respectively.With the increase of corrosion time,the corrosion phenomenon of aluminum-aluminum self-piercing riveting specimens is gradually serious,and the mass loss is gradually increasing.The average corrosion rate first increases and then decreases.After the static tensile test,the failure forms are all rivet pull-off failure,the mechanical strength gradually decreases,and the energy absorption value increases first and then decreases.The corrosion products are sulfate hydrates of Al₂O₃ and Al.With the increase of corrosion time,the corrosion phenomenon of steel-aluminum self-piercing riveting specimens is gradually serious,and the quality loss is first.After increase,the average corrosion rate increases first and then decreases.After the static tensile test,there are three failure modes:rivet pull-off failure,rivet bottom pull-through failure,and rivet neck fracture failure.The static strength increases sharply when the corrosion time is 720h.The energy absorption value decreases sharply when the corrosion time is 720h.The S and O elements appear in the upper plate,and the corrosion products of the lower plate are sulfate hydrates of Al₂O₃ and Al.The corrosion behavior at 1080h is roughly the same as the simulation result.