Abstract: One of the key characteristics of granular material in dynamic processes is the ability to transition between solid-like and fluid-like states [1,2]. In the solid-like state, the effect of deformation rate is typically negligible, and the material can sustain shear. In the fluid-like state, however, the effect of shear rate cannot be ignored [3]. The solid-like, fluid-like, and transitional states of the material can coexist, and changes in external load and shear stress are often accompanied by changes in the material's volume. The solid-fluid transition can be modelled naturally using particle-scale numerical models such as the discrete element method (DEM) but for industrial processes, these methods become computationally intractable. Continuum methods on the other hand, are computationally tractable but there is currently no consensus among constitutive models to accurately describe the transition between the solid and fluid states within a single set of governing equations. In this work, we propose to use a GPU-based Material Point Method (MPM) as our continuum solver for large deformations to model the dynamic interaction between dry powder and rigid body obstacles, including the solid-fluid transition related to impacts. We will describe our approach for selecting and implementing a combination of constitutive laws that accurately captures the state transition in granular materials. The content presented in this talk has significant implications for the development of continuum modelling of granular materials in industrial processes where uniform flowability is crucial. By using the MPM and suitable constitutive laws, we aim to obtain accurate macroscopic predictions that can be useful for design and optimization of industrial particulate processes. References: [1] Luding, S., Jiang, Y., & Liu, M. (2021). Un-jamming due to energetic instability: statics to dynamics. Granular matter, 23, 1-41. [2] Marveggio, P., Redaelli, I., & di Prisco, C. (2022). Phase transition in monodisperse granular materials: How to model it by using a strain hardening visco‐elastic‐plastic constitutive relationship. International Journal for Numerical and Analytical Methods in Geomechanics, 46(13), 2415-2445. [3] Forterre, Y., & Pouliquen, O. (2008). Flows of dense granular media. Annu. Rev. Fluid Mech., 40, 1-24.