1. Prediction of Trimmed Edge Stretching Performance
PIs: Brad Kinsey and Yannis Korkolis, UNH
Jyhwen Wang, TAMU

2. 4. Prediction of Trimmed Edge Stretching Performance
Industrial Need and Relevance: Failure strains in the stretch bending fracture and edge cracking can be significantly lower
than predicted using classic methods such as the forming limit curve. The goal of the project is to understand the mechanism of edge stretching failure and create a Edge Stretching Limit (ESL), in particular with respect to pre-strained materials.
NSF I/UCRC Planning Meeting

3. 4. Prediction of Trimmed Edge Stretching Performance
Project Objectives:
Determine and validate the ESL,
Establish a methodology to predict the trimmed edge performance of pre-strained sheets, and
Identify key material properties, tooling geometries, and process factors affecting the ESL.
Korkolis, NUMISHEET, 2016
NSF I/UCRC Planning Meeting

4. 4. Prediction of Trimmed Edge Stretching Performance
Punch displ.: 18 mm (onset of 1st rupture)
Approach/Methodologies:
Perform hole expansion tests, including Digital Image Correlation, with various edge conditions created.
Machined
Sheared
Etc.
Assess the effect of material, e.g., plastic behavior, grain size distribution, phase constituents, etc. on ELS. RD
NSF I/UCRC Planning Meeting

5. 4. Prediction of Trimmed Edge Stretching Performance
Approach/Methodologies:
Pre-strain sheets using the custom machine available at UNH.
Conduct numerical simulations to assess the stresses in the ESL failure.
NSF I/UCRC Planning Meeting

6. 4. Prediction of Trimmed Edge Stretching Performance
2 cameras for 3D DIC
punch (260 kN cap.)
DIC Lamp
Die Set
blankholder
Deliverables:
ESL for various process parameters, e.g., material variables, tooling geometries, and process factors
Pre-strained ESL
Accurate material data based on conditions at the hole
Numerical simulation model
NSF I/UCRC Planning Meeting

7. 4. Prediction of Trimmed Edge Stretching Performance
Budget and Timeline: Estimated cost of the project is $400k for two years.
Task / Milestone
Year 1
Year 2
Year 3 Q1 Q2 Q3 Q4
ESL parameter testing
Pre-strain material
 Pre-strained ESL
 Material characterization
 Numerical model
NSF I/UCRC Planning Meeting

8. 4. Prediction of Trimmed Edge Stretching Performance
Discussion:
Are the industrial need and relevance accurately captured?
Are the objectives realistic and complete?
Are the approaches technically sound and appropriate?
Are there alternative implementation paths or better approaches?
Are the deliverables impactful to industrial partners?
Are the budget and timeline reasonable?
Are there conflicts with intellectual property or trade secrets?
List additional project specific questions are appropriate.
NSF I/UCRC Planning Meeting