On Springback Prediction In Stamping Of AHSS BIW Components Utilizing Advanced Material Models Ming F. Shi and Alex A. Konieczny United States Steel Corporation
Introduction Origin of Springback AHSS Springback Effect of Material Models on the Springback Prediction Examples of using Advanced Material Models in the Springback Prediction Accuracy Improvement Introduction of a Novel Large Deformation Tension and Compression Test Examples of Tension and Compression Data and Determined Advanced Material Model Parameters
Origin of Springback Material elastic recovery after forming Coupled with mechanical multiplying effects Stress Strain Elastic Recovery Mechanical multiplying
True stress, MPa Elastic Recovery, Cont d 11 1 9 8 7 6 5 4 3 2 1 AL HSLA34 DP78 DP98 DP59 1 2 3 4 5 6 True strain, %
True Stress (MPa) True Stress (MPa) True Stress (MPa) True Stress (MPa) Greater Bauschinger Effect for AHSS 4 3 2 1-1 -2-3 -4 DDQ.2.4.6.8.1 True Plastic Strain 6 4 2-2 -4-6 HSLA.2.4.6.8.1 True Plastic Strain 8 6 4 2-2 -4-6 -8 DP6.2.4.6.8.1 True Plastic Strain 12 DP78 8 4-4.2.4.6.8.1-8 -12 True Plastic Strain
True Stress (MPa) More Elastic Recovery for AHSS? DP78 Tension and Compression 1 5-5 -1 Test Data.2.4.6 Linear Elastic Unloading Total True Strain
Springback of AHSS
Springback of AHSS
Under-predicted Springback using the Isotropic Hardening Model Measurement Prediction DP98 DP98-1.4 mm
Hardening Models Initial Yield Surface Stress 2 Stress 1 Kinematic Hardening Isotropic Hardening Isotropic/Kinematic Hardening
Yoshida Combined Isotropic/Kinematic Hardening Material Model Based on two surfaces model f f ( σ α) Y S β ( B R) F( σ ) f α α β * o α * * β o P m 2 3) bd p p (2 3) ad α p a B R Y C, [( β]; β Yoshida Model with Original Hardening Law: R m( Rsat R ) p Yoshida Model with modified hardening law N N K( e p Ke R ) N N a B R Y B Y K( e p) Ke
True Stress (MPa) Yoshida Model vs. Isotropic Hardening Model 1 DP78 Tension and Compression 5-5 Experiment Yoshida Model.1.2.3.4.5-1 True Plastic Strain Isotropic hardening
Example 1: Springback Prediction Improvement using an Advanced Material Model Measured Springback Isotropic Hardening Model Yoshida Model
Example 2: DP6 Red: Isotropic Blue: Yoshida Black: Scan
Challenges in Determining Material Model Parameters 7 constitutive parameters in Yoshida Model 9 constitutive parameters in modified Yoshida Model Large deformation tension and compression test is required. Multiple loading cycles are required. Optimization algorithm is required to determine the parameters
Introduction of a Novel Tension-Compression Test Large deformation tension-compression Anti-Buckling in the width direction Anti-Buckling in the thickness direction Friction measurement
Tension-Compression Test
Tension-Compression Test, Cont d
Total Force, N Friction Force, N Tension-Compression Test, Cont d 125 1 75 5 25-25 -5-75 -1-125 DP98-L4 +5% Total Force Friction Force 4 3 2 1 2 4 6 8 1 12 14 16 18 2-1 -2-3 Time, sec
True Stress, MPa Example of Tension-Compression Test Data Full Cycle DP98-5-L2 +/-5% 125. 1. 75. 5. 25.. -.6 -.4 -.2-25..2.4.6-5. -75. -1. -125. True Plastic Strain
True Stress, MPa Example of Tension-Compression Test Data Strain Memory Cycle 98-5-L3+ 5% US#3 125 1 75 5 25-25 -5-75 -1-125.2.4.6.8.1 True Plastic Strain
Yoshida Model Parameters for DP78 Modied Yoshida Model Y (MPa) B (MPa) C m b (MPa) h K (MPa) N e 291.6 453.5 513.2 62.5 449.1.95 7..955.52 Original Yoshida Model Y (MPa) B (MPa) C Rsat (MPa) m b (MPa) 291.6 465.1 46.7 52.5 56.5 444.7.95 h
True Stress (MPa) Predicted and Tested Data from a Full Cycle Tension and Compression Test for DP78 15 1 5 -.6 -.4 -.2-5.2.4.6-1 -15 True Plastic Strain Experiment Original Modified
True Stress (MPa) Predicted and Tested Data from a Strain Memory Tension and Compression Test for DP78 1 Experiment 5 Original Modified.2.4.6.8.1-5 -1 True Plastic Strain
On Springback Prediction In Stamping AHSS Thank you for your attention