Modelling of an Impact Wrench for Use in Reducing Hand-Arm Vibrations

Background: 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. Methods: A practical, low-order bond graph model of impact-wrench dynamics is developed, capturing interactions among the motor, hammer, anvil, and hand/arm constraints. The model is validated against measurements during bolt setting in a steel plate. Results: Predictions match measured RMS accelerations and spectral modes up to 200 Hz with errors within 11%. Analysis attributes the 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. Conclusions: The model provides physical insight into vibration origins and supports actionable design decisions (e.g., eliminating the linear impact, adding rotational damping/control) consistent with ISO 28927-13:2022 testing practice.