Dynamic response of muscle tissue under waterjet impact based on a visco-hyperelastic constitutive model considering...

Waterjet is increasingly used in medicine for cutting and ablation of muscle tissue due to its advantages of no thermal damage. However, accurate simulation and parameter optimization of waterjet-muscle interaction largely depend on a constitutive description that can capture both the nonlinear large-deformation behavior and the time-dependent relaxation of muscle tissue under impact loading. In this study, an improved visco-hyperelastic constitutive model for muscle tissue was developed by coupling the yeoh hyperelastic model with a two-term prony series generalized maxwell model, which can simultaneously capture both strain-stiffening and time-dependent stress relaxation of muscle tissue. Subsequently, a coupling framework of smoothed particle hydrodynamics-finite element method (SPH-FEM) based on the visco-hyperelastic constitutive model was established to simulate the dynamic response of muscle tissue under waterjet impact. To evaluate the model, waterjet impact experiments were conducted on fresh porcine muscle specimens using high-speed imaging to record tissue deformation and failure processes. The results showed that the model effectively described the nonlinear strain-stiffening and time-dependent relaxation behaviors of muscle tissue and reproduced the pressure-dependent evolution of impact depth, damage width, and separation rate under waterjet loading. The simulations indicated an onset of appreciable tissue separation around 0.4 MPa, above which impact depth increased markedly with impact pressure, whereas the damage width showed a comparatively smaller increase. In the tested pressure range, the SPH-FEM predictions showed good agreement with the separation-rate measurements derived from high-speed imaging, with relative errors below 10%. These results provide both a constitutive and numerical framework for predicting pressure-dependent soft-tissue separation under waterjet impact, and offer support for parameter optimization and low-trauma medical waterjet cutting applications.