The Discrete Continuum Method Based On ABAQUS And Its Application In Size Effects

With the rapid development of micro-nano technology,many micro materials such as micro-nano devices,micro-particles and micro-fiber reinforced composite materials are widely used.The mechanical behavior of microscopic materials exhibits significant size effects.Traditional macroscopic models don't contain parameters of characteristic length,which are no longer applicable to microscopic materials.Therefore,it is necessary to develop new research methods to correctly evaluate the mechanical behavior of microscopic materials and provide reliable designs for microstructures.Discrete dislocation dynamics simulation directly takes dislocation lines as the research object,simulates the movement and evolution of dislocations,and predicts the plastic deformation of microscopic materials from the physical nature.It is a very efficient research method at the microscopic scale.However,for problems including non-periodic boundary conditions such as micro-column compression,pure DDD method has certain limitations.In this paper,the user-defined element subroutine provided by ABAQUS is used to implement the discrete continuous method inside ABAQUS.The algorithm is used to simulate the micro-pillar compression of nickel single crystal materials,which make senses in exploring the mechanical behavior and internal mechanism of microscopic plastic deformation.In this paper,based on the discrete continuous method,the influence of plastic strain caused by dislocations is directly incorporated into the element control equation,and a userdefined element with the function of calculating the dynamics of discrete dislocations is designed.Data exchange between two modules are completely finished inside ABAQUS.At the same time,the plastic strain distribution of the dislocation nodes near the surface and the stress field near the dislocation core are modified to ensure that the calculation results are more in line with objective facts.The DCM method based on UEL is applied to simulate the compression of micropillars of nickel single crystal material under monotonic load.The stress-strain curve of nickel single crystal micro-pillars and the evolution of dislocation density are analyzed.Further researches were conducted to reveal the mechanism that grain orientation,initial dislocation density and model feature length affect the mechanical properties of nickel single crystal micro-pillars under monotonic load.The DCM method based on UEL is applied to simulate the tensile and compression of nickel single crystal materials under cyclic loading.Further researches were conducted to reveal the mechanism that grain orientation,initial dislocation density and model feature length affect the mechanical properties of nickel single crystal micro-pillars under cyclic load.