An investigation on characteristics of the vibration transmitted to wrist and elbow in the operation of impact wrenches

Abstract

To help assess the risk of the vibration exposure during impact wrench operation and to develop a convenient and effective method to monitor and control the exposure, this study aims to investigate the characteristics of the vibrations transmitted to the wrist and elbow in the operation and to evaluate the on-the-wrist and on-the-elbow vibration measurement methods. Six subjects participated in the experiment. Each of them used 15 impact wrenches on a simulated workstation. Tri-axial accelerations at three locations (tool handle, wrist, and elbow) and the tool effective torques were measured and used in the evaluations. Results confirm that the severity of the vibration exposure generally depends on tool and individual, and that the vibrations measured at wrist and elbow reflect the influences of both factors. This study also found that the accelerations measured at the wrist and elbow are correlated with the ISO frequency-weighted tool acceleration. The fundamental resonance of the hand-arm system in the range of 16–50 Hz is well reflected in the vibration measured at the wrist. The results also demonstrate that vibration exposure duration can be reliably detected from the wrist vibration data. Moreover, the wrist vibration is suggestively correlated with the torque of the pneumatic impact wrenches. These findings suggest that the measurement of the wrist vibration can be used as an alternative approach to perform the exposure risk assessment and to monitor and control the exposures in the operation of the impact wrenches. Relevance to Industry Impact wrenches or nut runners with impact action are widely and intensively used in automobile manufacturing and repair, which could generate significant vibration and require forceful actions. Prolonged, intensive exposure to both vibration and forceful actions could result in hand-arm vibration syndrome and carpal tunnel syndrome. The results of this study suggest that the on-the-wrist vibration measurement is a reasonable alternative approach for quantifying and assessing the exposures, which provides a theoretical base for developing a convenient and effective method for monitoring and controlling the combined exposures. The results of this study also suggest that the on-the-wrist method can also be used at workplaces to perform screening tests of the tools with dominant vibration frequencies similar to those of the impact wrenches and to evaluate the effectiveness of the anti-vibration devices used with such tools.