Investigation On Failure Behavior Of Titaniμm Alloy Rivet In Electromagnetic Riveting

Electromagnetic riveting is one of the applications of electromagnetic forming technology, and is μsed widely in aircraft structure parts. Under the impact loading, the deformation of rivet head is severe and it is easy to produce failure. The riveting quality is difficult to meet the requirement of the riveting process. In order to control the quality of riveting, the failure behavior of TA1 and TC4 tiataniμm alloy rivets is investigated using the combined research method of nμmerical simulation and experiment from the macro and micro scales in electromagnetic riveting.Electromagnetic riveting belongs to the high-speed loading, and the essential difference with normal riveting is the different loading rate. Loading speed measuring system of electromagnetic riveting is developed based on STC89C52 SCM and photoelectric sensor and is calibrated by coding motor. By the experiment of electromagnetic riveting speed test, the relationship between the discharge voltage and riveting die average loading rate is obtained.The deformation of rivet is simulated in electromagnetic riveting by ABAQμS. The effects of loading rate and riveting die type on rivet deformation are investigated. The results show that the rivet deformation is mainly composed of overall upsetting and local free upsetting. The higher the loading rate, the greater the stress of upsetting head is. Under the rivet die cavity constraint, the upsetting-head stress is larger than that of the flat head rivet. Maximum deformation zone move towards the direction of, rivet shaft. The deformation of upsetting-head is relatively uniform and the generation of crack can be controlled effectively.Under the unconstrained and split die constrainted, different loading rate process experiments are carried out respectively. The results show that the split die constrainted can improve material deformation. Under the condition of quasi static, the upsetting-head deformation of TA1 sample is uniform and the forming quality is good. In electromagnetic riveting process, the upsetting-head occurs surface crack. With angle and cup head die, the rivet material flow can be effectively improved and the crack problem of TA1 rivet head also can be solved. TC4 sample has poor plasticity and can not be deformed at room temperature. Hot riveting can solve the crack problem in rivet head of TA1 and TC4 rivet. At the same time, the 10 mm TA1 and TC4 samples in diameter can be deformed in the hot riveting experiment, so the hot riveting can solve the problem of large diameter rivet forming.The results of microscopic analysis of samples in different forming process show that the material deforms severely and plastic deformation proceeds by the way of adiabatic shear. The higher the loading rate, the more obvioμs the adiabatic shear band is. Holes are initiated and propagated in adiabatic shear band and the failure occurs ultimately. The crack morphology is different under different loading rate.The higher the loading rate, the more obvioμs the toughening is. And with the temperature increase, the crack of adiabatic shear in the upsetting-head can be controlled effectively.