Numerical Analysis of the Percussive Riveting Process

The Aerospace industry requires final assembly techniques that have high throughput. Riveting has been recognized and implemented for several decades where manufactured joints exhibit consistently high fatigue strength. The dynamic Percussive riveting process is a widely implemented process that produces high-quality joints in the aerospace industry. Portable equipment adds to ease of implementation of this process on the work-floor. A pneumatic rivet gun and bucking bar are used to form the rivet from opposite ends. The rivet gun supplies impact energy input into the rivet at a fixed frequency. After this riveting process plastically deforms the rivet, residual stresses are setup which hold the stackup together. The countersunk rivet is a commonly used rivet that provides the flushness demanded by aerodynamic requirements.

Dynamic modeling efforts published so far exist only in the field of automation studies. Residual stress field studies only exist for the squeeze riveting process. Automation studies made simplifying assumptions on the rivet deformations. A thorough understanding of the rivet deformation inside the stackup is essential to study the evolution of residual stresses and to estimate the joint fatigue strength of the percussive riveting process. Because the boundary conditions are different in squeeze riveting and the percussive riveting process and thermal effects are neglected in the studies focusing on the former process, we consider this effort to be separate from other existing squeeze riveting studies.

We will describe our numerical analysis efforts that aid understanding of the percussive riveting process. Theoretical estimates of the residual stress distribution at the rivet-hole interface will be discussed. Residual stresses setup inside the countersunk stackup during the squeeze riveting process will be compared with stresses setup during the percussive riveting process. Residual stress trends from the analysis of these two riveting techniques will be compared with the theoretical stress distribution.