The paper by Kenneth Hunt and Erskine Crossley explores the interpretation of the coefficient of restitution (COR) as damping in vibroimpact. They critique the Kelvin-Voigt model, which assumes that the relative motion during impact is a half sine wave, arguing that this model leads to physically impossible scenarios, such as tension between bodies before separation and an energy loss proportional to the square of the impact velocity. Instead, they introduce a damping term \(\alpha v_i^2\) and derive a more accurate model based on Hertz's theory for localized normal and frictionless contact. The authors show that their model is a special case of the Kelvin-Voigt model when impacts are absent and that physical experiments support their findings. They also discuss the limitations of the classical definition of COR and propose a more realistic hysteresis loop that aligns with the behavior observed in impact tests. The paper concludes with a detailed analytical formulation and numerical simulations, demonstrating the effectiveness of their model in predicting the response of vibroimpact systems.The paper by Kenneth Hunt and Erskine Crossley explores the interpretation of the coefficient of restitution (COR) as damping in vibroimpact. They critique the Kelvin-Voigt model, which assumes that the relative motion during impact is a half sine wave, arguing that this model leads to physically impossible scenarios, such as tension between bodies before separation and an energy loss proportional to the square of the impact velocity. Instead, they introduce a damping term \(\alpha v_i^2\) and derive a more accurate model based on Hertz's theory for localized normal and frictionless contact. The authors show that their model is a special case of the Kelvin-Voigt model when impacts are absent and that physical experiments support their findings. They also discuss the limitations of the classical definition of COR and propose a more realistic hysteresis loop that aligns with the behavior observed in impact tests. The paper concludes with a detailed analytical formulation and numerical simulations, demonstrating the effectiveness of their model in predicting the response of vibroimpact systems.