1. Effects of Residual Stress on Springback and Part Performance Brad Kinsey University of New Hampshire
UNH - 28 October 2016
Sheet Metal Forming

2. Objective and Technical Benefits
Objectives:
Develop effective methodologies to characterize residual stress and springback
After forming but still in tooling
After release from tooling
Zecevic and Knezevic, JOM, 2017
Coupled elasto-plastic self-consistent crystal plasticity model of cup drawing, AA6022-T4
TD=Z
RD=X
TD=Z
RD=X
Technical Benefits:
Improved dimension accuracy and structure performance of formed parts
Examples include springback after stamping in automotive industry and collapse of well casing (tube) after hydraulic fracturing
Improved product quality and reduced costs
UNH - 28 October 2016
Sheet Metal Forming

3. Technical and Non-Technical Obstacles
NIST, Center for Neutron Research
Residual stress measurement methods
Neutron diffraction
X-ray diffraction
Hole drilling, strain gauge
Cup drawing, split ring test
Limitations in residual stress measurements
Specimen size
Spatial resolution
Destructive methods
Required for accurate prediction in FEA
Constitutive modeling, including material anisotropy
Loading-unloading behavior of material
Gréze et al., IJMS, 2010
UNH - 28 October 2016
Sheet Metal Forming

4. Path to Implementation
Korkolis, unpublished
DQSK
DP 590
Investigate the residual stress and springback in:
Air bending
Stretch/draw bending
Cup drawing
Evaluate strain-relief methods
Comparison of experiments with numerical simulation results
Expand to roll forming of long, tubular products; stamping of automotive parts; and manufacturing of metal containers
UNH - 28 October 2016
Sheet Metal Forming

5. Discussion Topics Timing: priority, resources available when needed?
Obstacles: technical & business?
Resources: level, type & issues?
Anything missing for active industry support?
Estimated benefits realistic & complete?
Technical and non-technical obstacles complete or over reaching?
Alternative implementation paths or better approaches?
Conflicts with intellectual property or trade secrets?
NHBB, residual stresses
UNH - 28 October 2016
Sheet Metal Forming