The effects of feed force on rivet bucking bar vibrations.

Percussive riveting is the primary process for attaching the outer sheet metal "skins" of an aircraft to its airframe. Workers using manually-operated riveting tools (riveting hammers and rivet bucking bars) are exposed to significant levels of hand-transmitted vibration (HTV) and are at risk of developing components of hand-arm vibration syndrome (HAVS). To protect workers, employers can assess and select riveting tools that produce reduced HTV exposures. Researchers at the National Institute for Occupational Safety & Health (NIOSH) have developed a laboratory-based apparatus and methodology to evaluate the vibrations of rivet bucking bars. Using this simulated riveting approach, this study investigated the effects of feed force on the vibrations of several typical rivet bucking bars and that transmitted to the bucking bar operator's wrist. Five bucking bar models were assessed under three levels of feed force. The study results demonstrate that the feed force can be a major influencing factor on bucking bar vibrations. Similar feed force effects were observed at the bucking bar operator's wrist. This study also shows that different bucking bar designs will respond differently to variations in feed force. Some bucking bar designs may offer reduced vibration exposures to the bar operator's fingers while providing little attenuation of wrist acceleration. Knowledge of how rivet bucking bar models respond to riveting hammer vibrations can be important for making informed bucking bar selections. The study results indicate that, to help in the appropriate selection of bucking bars, candidate bar models should be evaluated at multiple feed force levels. The results also indicate that the bucking bar model, feed force level, or the bucking bar operator have no meaningful effects on the vibration excitation (riveting hammer), which further suggests that the test apparatus proposed by NIOSH researchers meets the basic requirements for a stable vibration source in laboratory-based bucking bar vibration assessments. This study provides relevant information that can be used to help develop a standardized laboratory-based bucking bar evaluation methodology and to help in the selection of appropriate bucking bars for various workplace riveting applications. RELEVANCE TO INDUSTRY: Because the feed force level can affect HTV exposures to bucking bar operators, the feed force required for specific riveting operations should be an important consideration when selecting bucking bar models. This study provides useful information about bucking bar responses to riveting hammer vibrations; this knowledge can improve bucking bar selections.