The effects of feed force on rivet bucking bar vibrations

Abstract

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.

A Review of Hand–Arm Vibration Studies Conducted by US NIOSH since 2000

“…Besides the modeling studies, we also conducted many experimental studies for testing and evaluating powered hand tools [ 143 – 150 ], which have been used not only to develop or improve the tool test standards but also to help select tools. NIOSH researchers have developed a dataset that includes vibration emissions of many hand-held powered tools ( https://www.cdc.gov/niosh/topics/noise/noise_levels.html (accessed on 9 June 2021).…”

“…Because bucking bars are not powered hand tools, no standard test method has been established. To help evaluate the effectiveness of vibration-reduced bucking bars and related VR devices, a testing method has been proposed [ 150 ]; its test rig is shown in Figure 13 .…”

“… A proposed bucking bar test rig [ 150 ], which is composed of the following components: (i) A remote-controlled pneumatic riveting hammer programmed to deliver consistent vibration stimuli; (ii) An energy absorber for dampening the vibration input to the simulated rivet; (iii) A simulated rivet; (iv) A force plate for measuring the ground reaction force (feed force); and (v) A computer monitor for displaying the applied feed force as a strip chart allowing the bucking bar operator to maintain the target force within the specified range. The tested bucking bar is pressed against the simulated rivet by a test subject.…”

Accurate mathematical modeling and experimental verification of impact riveting

“…Wang 6 investigated the riveting process with a statistical analysis method combined with a neural network to verify the riveting quality. McDowell 7,8 studied the vibrations of the rivet hammer and bucking bar to evaluate the level of HTV (Hand-Transmitted Vibration) on operators. Ahn 9 studied the evaluation method for human stress-factors of percussive riveting, and a pneumatic riveting test platform was constructed to conduct the riveting experiments.…”