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Research Papers

Cyclic Sheet Metal Test Comparison and Parameter Calibration for Springback Prediction of Dual-Phase Steel Sheets

[+] Author and Article Information
Bin Gu, Yuan Chen, Yongfeng Li

State Key Laboratory of Mechanical
System and Vibration,
Shanghai Key Laboratory of Digital
Manufacture for Thin-walled Structures,
Shanghai Jiao Tong University,
Shanghai 200240, China

Ji He

State Key Laboratory of Mechanical
System and Vibration,
Shanghai Key Laboratory of Digital
Manufacture for Thin-walled Structures,
Shanghai Jiao Tong University,
Shanghai 200240, China
e-mail: benbenhj@sjtu.edu.cn

Shuhui Li

State Key Laboratory of Mechanical
System and Vibration,
Shanghai Key Laboratory of Digital
Manufacture for Thin-walled Structures,
Shanghai Jiao Tong University,
Shanghai 200240, China
e-mail: lishuhui@sjtu.edu.cn

1Corresponding authors.

Manuscript received March 14, 2017; final manuscript received May 29, 2017; published online July 14, 2017. Assoc. Editor: Gracious Ngaile.

J. Manuf. Sci. Eng 139(9), 091010 (Jul 14, 2017) (14 pages) Paper No: MANU-17-1148; doi: 10.1115/1.4037040 History: Received March 14, 2017; Revised May 29, 2017

Springback is an important issue for the application of advanced high-strength steels (AHSS) in the automobile industry. Various studies have shown that it is an effective way to predict springback by using path-dependent material models. The accuracy of these material models greatly depends on the experimental test methods as well as material parameters calibrated from these tests. The present cyclic sheet metal test methods, like uniaxial tension–compression test (TCT) and cyclic shear test (CST), are nonstandard and various. The material parameters calibrated from these tests vary greatly from one to another, which makes the usage of material parameters for the accurate prediction of springback more sophisticated even when the advanced material model is available in commercial software. The focus of this work is to compare the springback prediction accuracy by using the material parameters calibrated from tension–compression test or cyclic shear test, and to further clarify the usage of those material parameters in application. These two types of nonstandard cyclic tests are successfully carried out on a same test platform with different specimen geometries. One-element models with corresponding tension–compression or cyclic shear boundary conditions are built, respectively, to calibrate the parameters of the modified Yoshida–Uemori (YU) model for these two different tests. U-bending process is performed for springback prediction comparison. The results show, for dual phase steel (DP780), the work hardening stagnation is not evident by tension–compression tests at all the prestrain levels or by cyclic shear test at small prestrain γ = 0.20 but is significantly apparent by cyclic shear tests at large prestrain γ = 0.38, 0.52, 0.68, which seems to be a prestrain-dependent phenomenon. The material parameters calibrated from different types of cyclic sheet metal tests can vary greatly, but it gives slight differences of springback prediction for U-bending by utilizing either tension–compression test or cyclic shear test.

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References

Figures

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Fig. 1

Stress–strain curves of DP780 along different directions under uniaxial tension

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Fig. 2

Stress–strain curve of DP780 subject to loading-unloading-reloading uniaxial tension

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Fig. 3

The degradation of Young's modulus with the plastic strain for DP780

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Fig. 4

Specimen dimensions: (a) in-plane uniaxial tension–compression test specimen (TCT-specimen) and (b) in-plane cyclic shear test specimen (CST-specimen)

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Fig. 5

The strain paths of TCT-specimen and CST-specimen

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Fig. 6

Experiment setup for tension–compression test and cyclic shear test: (a) the universal cyclic test platform, (b) the schematic diagrams of the clamping device, and (c) the modified back clamping plate for cyclic shear test

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Fig. 7

The strain measurements methods for (a) tension–compression test and (b) cyclic shear test

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Fig. 8

Shear angle definition

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Fig. 9

The boundary conditions of one element models for (a) tension–compression test and (b) cyclic shear test

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Fig. 10

The flow chart of material parameter calibration by ls-opt

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Fig. 11

The experimental apparatus for U-bending

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Fig. 12

The schematic diagrams of U-bending test: (a) dimensions of the specimen, (b) dimensions of the U-bending tools, and (c) finite element model for U-bending

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Fig. 13

Influence of friction coefficient on punch force versus displacement curves of U-bending test

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Fig. 14

Frictional correction for uniaxial tension test: (a) force–displacement curve and (b) stress–strain curve

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Fig. 15

Cyclic stress–strain curves after friction corrections for (a) tension–compression test and (b) cyclic shear test

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Fig. 16

The equivalent stress–strain curves for uniaxial tension test and simple shear test

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Fig. 17

The equivalent stress–strain curves under reverse deformations for cyclic tests at different prestrains based on Hill’48 planar anisotropic yield function

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Fig. 18

Cyclic true stress–strain curves from different sets of parameters obtained from: (a) each single curve, (b) prestrain = 0.03, (c) prestrain = 0.05, (d) prestrain = 0.07, (e) prestrain = 0.09, and (f) uniaxial tension + prestrain = 0.03 + 0.05 + 0.07 + 0.09

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Fig. 19

Cyclic shear stress–strain curves from different sets of parameters obtained from: (a) each single curve, (b) prestrain = 0.20, (c) prestrain = 0.38, (d) prestrain = 0.52, (e) prestrain = 0.68, and (f) simple shear + prestrain = 0.20 + 0.38 + 0.52 + 0.68

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Fig. 20

The results of U-bending test

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Fig. 21

The stress states of element #9958 at sidewall after drawing: (a) the evolution history of σx for integration point 1 and (b) the magnitudes and distributions of Δσx for the seven integration points over the thickness compared to isotropic hardening

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Fig. 22

Cyclic curves for: (a) simulations of the tension–compression test with cyclic shearparameters and (b) simulations of the cyclic shear test with tension–compression parameters

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Fig. 23

Cyclic curves for: (a) simulations of the full cyclic tension–compression test with half-cyclic parameters and (b) simulations of the multiple cyclic shear test with half cyclic parameters

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