Contact forces and motion behavior of non-Newtonian fluid-solid food by coupled SPH-FEM method

The non-Newtonian fluid-solid interaction food has complex physical properties and complicated contact force, which brings the greater technical challenge to improving the food fetching rate. In this work, we used the smooth particle hydrodynamics and finite element coupling method for a node-to-surface penalty function contact to characterize the contact forces between non-Newtonian fluid food and solid foods. The shear rheological properties and density of non-Newtonian fluid food, including xanthan gum (XG) and guar gum (GG), were investigated by a viscometer and densitometer, respectively. The results showed that the shear viscosity of non-Newtonian fluid food depends to some extent on the mass ratio of the thickening gums. We investigated the effects of the end-effector with different fetching velocities and different inclination angles, and the nut root powder paste (NRPP) food with different ratios of XG and GG, on the fetching rate, stress-strain, and motion behavior. The results showed that the stress increased with increasing v(1) and w; however, the v(2) had less effect on the stress. The sparseness of the distribution of solid food was related to the v(1) and w, whereas it was less influenced by the v(2). The distribution of solid food became denser in the X-Z plane and sparser in the X-Y plane with increasing inclination angle. The motion behavior of viscoelastic solid foods depended on the mass ratio of XG to GG dissolved in NRPP. The present work can provide a theoretical foundation for meal-assisting robots and robots in the field of food engineering with the task of improving the food fetching rate.