Crystal Plasticity Constitutive Modeling And Simulation For TA2 Sheet Mechanical Behavior And Microchannel Forming

In the context of resource scarcity and environmental degradation,and the hydrogen fuel cell has emerged as one of the most promising power equipment thanks to its outstanding characteristics of being clean and efficient.The metal bipolar plate is the basic structural element of a hydrogen fuel cell,and one of the primary forming processes used for the plate is plastic stamping technology.Fewer grains are present in the area where ultra-thin plates form,which strengthens the relationship between the material’s microstructure and its macroscopic mechanical performance.The traditional macroscopic phenomenological constitutive model cannot accurately describe the influence of microstructure information on the formability and hardening behavior of sheet metal.Therefore,it is of great significance to fully understand the nature of plastic deformation and explore the internal mechanism of forming for realizing the accurate forming of sheet metal.The crystal plasticity theory,which adds deformation mechanisms like dislocation slip to the constitutive framework for explaining the plastic deformation of materials,fully accounts for the strong link between crystal structure and forming properties.The macro-mechanical response of materials is composed of the response of a single grain.This study uses TA2 sheet,which has high strength,great corrosion resistance,and a light-specific gravity,to create a metal plate using stamping and forming techniques.At room temperature,TA2 is a typical metal with close-packed hexagonal lattice structure,there are few slip systems that can be started,so it is necessary to start twin systems to assist the deformation.However,the current research on crystal plasticity theory only considers the contribution of dislocation slips to plastic forming behavior.It is important to further understand the influence of twinning behavior on plastic deformation behavior.This study combines theoretical modeling,simulation,and experimental verification based on the theoretical basis of crystal plasticity that includes twinning to address the dimensional effects,anisotropy,and strain hardening in plastic formation of TA2 sheets from a microstructure viewpoint.Firstly,Based on the properties of TA2’s crystal structure,a crystal plastic constitutive model based on slip and twinning deformation process is created.A hardening model taking twinning into account is introduced to describe the evolution of slip and twinning resistance in the constitutive structure relationship,which is used to reveal the dependence of the macroscopic deformation behavior of close-packed hexagonal metals with twinning and slip as deformation modes on the evolution of the microscopic weave.This helps to explain the strain-hardening and softening behavior caused by slip and twinning in material deformation.Secondly,a three-dimensional polycrystalline finite element model with true grain morphological features was built based on EBSD characterization experiments in order to reconstruct the real microstructure morphology of the raw material in its original state.Crystallographic features including grain shape,grain size,and weave information can be obtained via EBSD characterisation tests.Then the data was processed using the MTEX toolbox,the RVE model was developed in ABAQUS based on the Python to recreate the real particle shape.By using MATLAB to process crystal orientation information and convert it into material property files,the material properties can be assigned in batch by rewriting the inp file so that the grain regions can obtain the corresponding orientation information to realize the construction of polycrystalline RVE models in ABAQUS.Then,the effect of micro structure on the deformation behavior of metals with closepacked hexagonal lattice structures is investigated.This study examines the impact of crystal orientation,deformation mode,and size influence on the non-uniform stress-strain response of TA2 plastic deformation.Uniaxial tensile tests were performed on 0.1 mm TA2 ultrathin plates with various grain sizes,followed by polycrystalline RVE models with various grain sizes and finite element simulations combined with the crystal plasticity theory of coupled twin deformation mechanism.The outcomes demonstrate that there is a significant size effect in both experimental and simulation results,that the varying crystal orientation and twinning activity is one of the significant factors for the inhomogeneity of plastic deformation,and that the twinning layer prevents the motion of dislocation slip and thereby increases the material strength.As a result,the results also demonstrate that the mechanical behavior of the material is closely related to the microstructure.Ultimately,micro-channel stamping and forming experiments along with crystal plasticity finite element simulation were designed to examine the influencing elements of micro-channel forming in order to better understand the deformation behavior of ultrathin titanium plates at micro mesoscopic scale.By analyzing the formed sample’s plate thickness thinning and forming depth in order to quantify the quality of the formed plate,it was discovered that lubrication conditions,dimensional effects,and crystal anisotropy all had a significant impact on that quality.A comparison of the experimental and simulation results shows that the polycrystalline micro-channel forming model combined with the crystal plasticity constitutive model is a more accurate method than the conventional finite element model to reflect the influence of microstructure on micro-channel forming.