Modeling of an Impact Wrench for Use in Reducing Hand–Arm Vibrations

Impact wrenches are widely used in construction and automotive industries, yet they generate harmful vibrations that pose health risks to operators and reduce tool usability. This paper develops a practical, low-order bond-graph model of impact-wrench dynamics that captures interactions among the motor, hammer, anvil, and hand/arm constraints, and validates it against measurements during bolt tightening into a steel plate. Predictions match measured RMS accelerations and spectral modes up to 200 Hz with a maximum relative RMS error of 11%. The analysis attributes dominant vibration sources to rotational and translational impacts between the hammer and anvil; notably, the translational (z-axis) impact contributes substantially to felt vibration while not being required for bolt tightening. The model provides physical insight into vibration origins and supports actionable design decisions, such as reducing the linear (z-axis) impact and adding rotational damping or control, consistent with standardized testing practice.