High-speed abrasive water jetting is an alternative tool for machining engineering materials. The energy dissipation processes involved in this erosion process have not been investigated systematically. In this paper, a model is developed to calculate the energy dissipation in workpieces eroded by abrasive water jets; By introducing an energy dissipation function chi(Phi), the model enables the estimation of the energy absorption as a function of the erosion depth. The energy dissipation function can be expressed by a second-order polynomial approximation. Measurements of the reaction forces on the exiting slurry after the erosion process, material removal experiments and fracture tests are conducted to separate the components of the energy dissipation parameter, such as damping, friction and erosion debris generation.