Study on Nonuniform Deformation of Tailor Rolled Blank During Uniaxial Tension

The deformation characteristics of tailor rolled blank （TRB） in the course of uniaxial tension were studied by means of analysis, test and simulation. The mechanical analytical model of TRB during uniaxial tension was set up, and the deformation formulae for the thinner side and for the thicker side were derived to quantify the deformation of TRB. On this basis, uniaxial tension tests on TRB and ordinary blanks （the thinner side and the thicker side of TRB） were conducted. Lagrange polynomial interpolation method was adopted to construct the stress-strain fields of unannealed and annealed TRBs for solving TRB material parameters, and then, uniaxial tension simulation on TRB was completed. Deformations and properties of unannealed TRB were compared with those of annealed TRB, and the thinner side and the thicker side were also compared. Finally, the research results were explained by metallurgical structure. The results show that nonuniform deformation happens in TRB during uniaxial tension, and the necking occurs on the thinner side. The agreement of analysis, test and simulation confirms the correctness of the analytical model and the deformation formulae. The findings of this paper can lay the foundation for the future study on TRB stamping formability and provide a way for TRB modeling.

Forming Limit and Thickness Transition Zone Movement for Tailor Rolled Blank during Drawing Process

The process of automobile lightweight can be promoted by the application of tailor rolled blank（TRB）in the automobile industry.Therefore,research on the formability of TRB is of good practical significance and application value because of the enormous potential of TRB in the aspect of automobile lightweight.Aiming at the present condition of lack of researches on the influence of characteristic parameters on TRB drawing process,the drawing formability of TRB was studied with a combination method of simulation and experiment by taking square box as the research object.Firstly,drawing simulation and experiment of TRB were carried out.Then,effects of thickness transition zone（TTZ）position and blank size on the drawing formability of TRB were analyzed.Forming limit and TTZ movement for TRB square box during the drawing process were respectively discussed,when transition zones of TRB were located at different positions and blanks were of different sizes.The results indicate that lubrication condition exerts greater influence on TRB forming limit in comparison with TTZ movement,and the smaller blank size and TTZ being located at the blank center or slightly offset to the thinner side are preferable for acquiring greater forming limit and smaller TTZ movement.

Springback behavior of tailor rolled blank in U-shape forming

The springback of tailor rolled blanks with quenching and partitioning steels was investigated.In order to find out the springback behavior and related influence factors for the novel sheets,both experimental and simulation methods have been used to compare and analyze the springback characteristics of equal thickness blanks and tailor rolled blanks in U-channel forming.From the results,the overall springback angles of tailor rolled blanks at thin and thick sides are respectively 106.79° and 99.705°,which are both lower than those of the corresponding equal thickness blanks.Due to the existence of the thickness transition zone,the stress distribution in thin and thick sides of blanks is changed.The location of dangerous region in thin side of tailor rolled blanks is closer to the end of side,and the thick side moved to the middle of straight wall,which are different with the equal thickness blanks.Afterwards,the released quantitles of tangential stress and strain per unit section of blank are adopted to calculate relative springback angles and give novel evaluation criteria for qualitatively analyzing the amount of springback angles.By comparing the results,it shows that the tangential strain method is more suitable for the actual situation.

Symmetric and Asymmetric Rolling Pure Copper Foil: Crystal Plasticity Finite Element Simulation and Experiments

A systematic study has been conducted aiming to attain an insight into the influence of coefficient of roll speed asymmetry, crystal orientation and structure on the deformation behavior, and crystallographic orientation development during foil rolling. Simulations were successfully carried out by using crystal plasticity finite element method（CPFEM）,and a novel computational framework is presented for the representation of virtual polycrystalline grain structures. It has been found that asymmetric rolling（ASR） is more efficient in producing plastic deformation since it develops additional shear strain and activity of slip system compared with symmetric rolling（SR）. For ASR, increase in the length of the shear zone, and decrease in the amount of the pressure and roll force would lead to further reduction. The shear strain path in SR and ASR is strictly influenced by the misorientation of neighbor grains, and corresponding {1 1 1} pole figures offer direct evidence of the spread of crystallographic orientation around the normal direction. The activity of slip systems was examined in detail and found that the predicted results are consistent with the surface layer model. The accuracy of the developed CPFEM model is verified by the fact that the simulated results of roll force coincide well with the experimental results.

A heterozygous mutation in GJA1 gene in Chinese family with serious erythrokeratodermia variabilis et progressive

To the Editor:Erythrokeratodermia variabilis (EKV;MIM 133200) is characterized by the coexistence of transient,figurate,erythematous patches,and localized keratotic hyperkeratosis.EKV shows marked phenotypic heterogeneity,even within kindreds bearing the same diseasecausing mutation.[1] The term EKV et progressiva (EKVP) is a severe variant of EKV and has been proposed to encompass the diversity of phenotypes,ranging from limited hyperkeratotic plaques and erythematous patches to severe progressive symmetric erythrokeratodermia which can feature more generalized cutaneous involvement.