Thermo-mechanical modeling of flow drilling with a conical-tipped blind rivet

Abstract

Flow drill riveting (FDR) is an advanced single-sided thermo-mechanical joining method which combines flow drilling and blind riveting. Accurate prediction of penetration force and torque during flow drilling is of significance to the optimization of process parameters and understanding of underlying mechanisms. The penetration force and torque during flow drilling are closely related to the yield strength of workpiece material (e.g. AA7075-T6 in this work), which depends on the temperature at contact interface between rivet and workpiece. An analytical thermal model was developed on the basis of the proposed energy partition coefficient ( k ), which represents the ratio of effective energy converted into increased temperature of workpiece to total energy consumed mainly by torque during flow drilling, and a maximum prediction error of the temperature was within 4%. In addition, the coefficient of friction at contact interface between rivet and workpiece is important to the theoretical calculation of penetration torque during flow drilling, and is greatly affected by the temperature at contact interface between rivet and workpiece. The relationship between the coefficient of friction and temperature was developed from the analytical thermal model. At the end of this work, the prediction models for penetration force and torque are established and verified through experiments.