Research On Plastic Deformation Behavior Of CR340 TRB By Using Crystalline Plasticity

Tailor Rolled Blank is another new lightweight blank after Tailor Welded Blank.Dueing to the different rolling degree of different thickness zones,there are diversity in microstructure such as grain shape,grain size and crystal orientation,which are macroscopically manifested as differences between mechanical properties and plastic deformation behavior in different thickness zones.Therefore,the forming theory based on a single thickness plate is no longer applicable to Tailor Rolled Blank.In this paper,a macro-microscopical coupling research method is applied to establish a polycrystalline plastic constitutive finite element model using crystal plasticity theory to study the influence rule of microstructure on the plastic behavior of Tailor Rolled Blank,to reveal the plastic flow behavior of micro-uneven blank,and to establish the universal law of flow performance of Tailor Rolled Blank.In this paper,the uniaxial tensile test was applied to analyze the differences of basic mechanical properties in different thickness zones of Tailor Rolled Blank.Then electron backscattering diffraction(EBSD)technique was used to test the basic microstructure information such as grain morphology,size and orientation in different thickness zones of the blank,so as to obtain the laws of microstructures affecting the macroscopic mechanical properties.The results show that both the thin and thick zones were composed of equiaxed grains,and the grain size distribution was uniform,which was macroscopically expressed equal thickness zones have good plastic deformation ability and excellent mechanical properties.However,the transition zone has uneven grain size distribution and poor microstructure uniformity.Therefore,necking occurs earlier and the toughness is poor.In addition,there is a typical favorable texture dominated by {111}<uvw> in the equal thickness zones,and there is no obvious favorable texture in transition zone.Applying the finite element software secondary development function of Abaqus,a polycrystalline plastic finite element model of Tailor Rolled Blank is established based on the micro-structure information to study the influence of the microstructure difference on plastic deformation behavior of Tailor Rolled Blank.In the neper,the polycrystalline geometric model was established using voronoi graphics method which was given the grain favorable texture of Tailor Rolled Blank.Then the crystal plastic finite element model conforming to the microstructure of Tailor Rolled Blank is established to simulate the micro-deformation behavior of Tailor Rolled Blank under macro-external forces.The results show that there are more grains in the equal thickness zones,and the plasticity of the material is higher than that in transition zone.There are more grains in the hard orientation in transition zone,which makes the stress concentration easier.The change of the position of the transition zone affect formability of Tailor Rolled Blank.In transition zone near thin zone,the stress and strain distribution of deformation zone is uneven.When the degree of loading becomes larger,the deformation area is more concentrated and the formability is lowered.In transition zone near thick zone,the stress-strain distribution in the deformation zone is relatively uniform.When the degree of loading becomes larger,the deformation zone is gently diffused and the formability is improved.Based on the above research results,the bending test and metallographic experiment were used to study the relationship between plastic deformation behavior,formability and thickness,microstructure of Tailor Rolled Blank.The results show that the grains in equal thickness zones are uniformly deformed and plastic deformation performance is good,but the grains in transition zone are only locally deformed and plastic deformation performance is poor.Transition zone of Tailor Rolled Blank is a key zone of plastic flow non-uniformity,resulting in the poor forming performance,which is shown as the high rebound value after bending.In transition zone near to thin zone,the plastic flow non-uniformity of the blank increases,the thinning rate increases,and the formability decreases.In transition zone near thick zone,the plastic flow non-uniformity is reduced,the amount of thinning is decreased,and the formability is improved.The experimental results are compared with the simulation results,which further validates the accuracy of the polycrystalline plastic finite element model of Tailor Rolled Blank.