Local Phenomena During Riveting Process

The paper presents experimental and numerical study of the local phenomena during the riveting process. It is commonly accepted that technological factors of the riveting process has a strong influence on the fatigue life of riveted joints. The authors analysed the papers concerned the experimental researches of the riveting force influence on fatigue life. The magnitude of the life increase caused by the riveting force increase suggests the authors that this is not only the result of beneficial stress system but the change of the joint formation mechanism has taken place. This was an inspiration to undertake more detailed researches of the riveting process. The strain progress during the riveting process has been experimentally investigated for four types of aluminium rivets used in airframes. Measurements confirm very high strains near the driven head. For some types of rivets the reversal strain signal has been recorded. Several FE model has been use to investigate the riveting process. The axisymmetric and solid models were used. The agreement of experimental and numerical results in some cases were good, in other cases the numerical models demand further development. In any calculations, the reversal strain effect has not been obtained, This suggest that it is result of the phenomenon which has not been taken into account in numerical modelling. The working hypothesis has been assumed that during the riveting process adhesive joints (called cold welding) were formed and destroyed during the process, what was the reason of the observed reversal strain signal. The authors are going to continue this investigation.