Experimental and numerical study of stress and strain field around the rivet

Abstract

The paper deals with determination of stress and strain field induced during riveting and FEM modelling of this process. Stress and strain measurements during riveting allow for better understanding the phenomena that occur during this process and to determining stress and strain field which exists in the joint after riveting. The results will be also used for validation of FEM models. Stress and strain measurements were carried out with the X-ray diffractometer and strain gauges on the sheet surface near the driven head. The investigation concerned sheets and rivets used in the Polish aerospace industry. This paper presents measurements results for two types of rivets; the brazier rivet (BN-70/1121-06) and the rivet with a compensator (OST 1 34040-79 1), as well as the FEM analyses results. Bare sheets made from 2024 T3 aluminium alloy with the nominal thickness of 1,27 mm and rivets with the diameter of 3 mm and 3,5 mm made from Polish aluminium alloy PA25 were used. The influence of squeezing force as well as the rivet type on stress and the strain system was investigated. Two types of strain gauges were used. The strip miniature gauges with the gauge length of 0,51 mm were located outside driven head and worked during the whole riveting process. The micro strain gauges with gauge length of 0,38 mm were applied very close to the rivet hole, in the area which is under the driven head after the the riveting process. The gauges recorded strain to the point when they were destroyed by the driven head. The measurements results were compared with the FEM results.