Evolution of Die Wear and Sheared Edge Parameters …/media/Files/Autosteel/Great...Effects of Tool...

GDIS2017

Evolution of Die Wear and Sheared Edge

Parameters in Trimming of DP980 Steel

Sergey Golovashchenko – Oakland University

Raj Sohmshetty – Ford Motor Company

#GDIS | #SteelMatters 2

Acknowledgements • Research Team at Oakland University

Saeid Nasheralahkami

Weitian Zhou

Scott Dawson

Daniel Kowalsky

Elizabeth Lekarczyk

Nan Wang

Sergey Golovashchenko

• Research Team at Ford

Lloyd Mason

Constantin Chiriac

Darryl Young

Raj Sohmshetty

• Research Team at US Steel

Brandon Hance

Ming Shi

• Research Team at AK Steel

Matt Folkner

Kavesary Raghavan

Yu-Wei Wang

• Research Team at PNNL

Guang Cheng

Kyoo Sil Choi

Xiaohua Hu

Xin Sun

• Sponsors: Ford, DOE VTO, FCA, NSF


Outline

• Introduction

• Traditional Trends in Trimming and Punching

• Mechanism of Fracture in Trimming of DP980

• Sheared Edge Stretchability for DP980 vs. DP600

• Die Wear Trend for Trimming of DP980

• Effect of Die Wear on Sheared Edge Stretchability

• Conclusions


Traditional Trends in Trimming and Punching

5% 10% 15% 20% 30% 40% 50%

Effect of Cutting Clearance on DP500 Edge

Cross-Sections of Trimmed Edges

DP500 Punching Data: Chintamani, J. and Sriram, S., "Sheared Edge Characterization of Steel Products used for Closure Panel Applications," SAE Technical Paper 2006-01-1589, 2006, doi:10.4271/2006-01-1589.


Traditional Trends in Trimming and Punching

5% 10% 20% 30% 40% 50%

10% Clearance 30% Clearance


Mechanism of Fracture in Trimming

DP600 Punching Data: Konieczny, A. and Henderson, T., "On Formability Limitations in Stamping Involving Sheared Edge Stretching," SAE Technical Paper 2007-01-0340, 2007, doi:10.4271/2007-01-0340.


Experimental Setup at Oakland University

Decoiler Straightener and

Automatic Feeder

65 ton Minster

Mechanical Press

Equipment Utilized During Experimentation


Mechanism of Fracture in Shearing of DP980

4%(t) 10%(t) 17%(t) 20%(t) 30%(t) 40%(t)

Effect of Cutting Clearance on Trimmed Edges

10%(t) Clearance 40%(t) Clearance



Evolution of Burrs on Trimmed Edge - DP980 Formation of Local Burrs On the Trimmed Edge of DP980

0

5

10

15

20B

urr

He

igh

t %

t

Locations

Clearance: 10%t

230K cuts

35K cuts

New Tool


Effects of Tool Wear on Sheared Edge

• The die wear test was conducted with 10% clearance

• After 35,000 cuts, the tool had some “wear”

• Experiments with various clearances were performed on

new tool and 35k/10% tool


Die Wear Trend in Sheet Metal Cutting Tools

P. Sartkulvanich and T. Altan

Examining edge cracking in hole flanging of AHSS

Stamping Journal October 2008

Typically, more wear is observed

from the upper cutting tool due

to excessive abrasion on the

sheared edge of the blank

during shearing and return

motions.

Multiple publications on punch

wear for punching round holes.


Die Wear After 230,000 Cuts of DP980 Sheet

5 mm Upper Trimming Tool

Sharp

Trimming

Edge

Uniform Abrasive Wear + Minor Microchipping in the Upper Tool

Severe Microchipping in

the Lower Tool

Burr and Burnish Height Evolution for

Trimming DP980 at 10%(t)

Lower Trimming Tool


Measurement of Trim Die Surface Profile

Roughness Profile After 230,000 Cuts

Material ratio curve

Ra=0.017mm (Average Roughness of A Surface)

Rz =0.134mm (Difference Between the Tallest

“Peak" and the Deepest “Valley")

Keyence VR3200 Profilometer


Correlation of Burrs and Chippings on Lower Die

Excellent correlation of local burrs on the trimmed sample with

the local chippings sites on the lower trimming tool

DP980 sheet

Lower D2 trim die


Methods for Sheared Edge Stretchability Study

• Hole Expansion

Test (ISO 16630)

• Tensile Test of

Samples with One

Sheared Edge

• Side-Bending Test

½ Dog Bone Strip


Hole Punching DP980 - 7% Clearance

Sheared edge after

hole punching


Sheared edge after

hole punching

Hole Punching DP980 - 24% Clearance


Hole Expansion Crack Location Comparison

DP 980 5% DP 980 24%


Results on Sheared Edge Stretchability of DP980

0.00

0.10

0.20

0.30

0.40

0.50

0% 10% 20% 30% 40% 50%

Bu

rr H

eig

ht

mm

Punching Clearance

DP 980 Hole Punching Burr Height


Equipment Used in Sheared Edge Study

Nikon SMZ745T – Pixelation Method

FMTI Grid Analyzer

Instron 5982 with 2D DIC system 2x Nikon DSLR with Macro Lens

Aramis System


Crack Formation for 5% Clearance - Tensile Test

No Visible Sources of Fracture

Cracks Forming in the Central Area

Cracks are Visible in Multiple Locations

Throughout the Thickness


Crack Formation for 5% Clearance - Side Bend Test


Cracks Forming in the Central Area

Cracks are Visible Throughout the Thickness

Including Burr Side and Burnish Side


Hairline Cracks Seen in Burr Zone

Macro Cracks Propagating from the Burr Zone




Burr Initially Formed But Broke From Edge

Cracks Appear To Form From Uneven Cavity

Cracks Propagate Into the Sample



Initial Imperfections on the Burr Side

Crack Formation

Noticeable Cracking From Burr Side



Initial Imperfections Noticed on the Burr Side

Crack Formation

Noticeable Cracking From Burr Side



Worn Tool Edge Condition (10% Clearance)

The Burr affected zone (broken

burr and burr formation) is 30%

of the gauge length.

If the localized necking

coincides with the burr affected

zone, the sample fails similarly

to the high clearance samples

(>20%), which have the entire

length affected by the burr.


Conclusions

• DP980 shows lower tendency to form burrs in

trimming due to breaking them off at the end of the

trimming process;

• Chipping of the lower die prevails as a die wear

mechanism for D2 inserts in trimming of DP980; and

• Avoiding burr formation helps to maintain sheared

edge stretchability of DP980 throughout the life of the

tool.


Conclusions - Continued

• Among reviewed methods to measure sheared

edge stretchability, in-plane side bending of the

strip with the sheared edge seems to have high

potential for industrial applications.


References

1. Chintamani, J. and Sriram, S., "Sheared Edge Characterization of Steel Products used for Closure Panel Applications,"

SAE Technical Paper 2006-01-1589, 2006, doi:10.4271/2006-01-1589.

2. Konieczny, A. and Henderson, T., "On Formability Limitations in Stamping Involving Sheared Edge Stretching," SAE

Technical Paper 2007-01-0340, 2007, doi:10.4271/2007-01-0340.

3. Coryell, J.J. “Edge Fracture in Mixed Microstructure Steels,” GDIS 2016

4. Zhou, D., Du, C., Hsiung, G., and Schmid, K. “Lessons Learned from Ultra High-Strength Steel Blanking,” GDIS 2015.

5. Golovashchenko, S.F. and Ilinich A.M., Analysis of trimming processes for stamped body panels, GDIS 2008.

6. Le, Q.B., deVries, J.A., Golovashchenko, S.F., and Bonnen, J.J.F., “Analysis of sheared edge formability of aluminum,“

Journal of Materials Processing Technology 214 (2014) 876– 891.

7. Nasheralahkami, S., Golovashchenko, S.F., Malek,C., Rugh, E., Kowalsky, D. and Zhou, W., “Sheared Edge Stretchability

of Steels Suitable for Automotive Applications,” SAE Paper 2017-01-1708.

8. Nasheralahkami, S., Golovashchenko, S.F., Dawson, S.A., Sohmshetty, R. “Analysis of Tool Wear for Trimming of DP980

Sheet Metal Blanks,” 2017 SAE International doi:10.4271/2017-01-0302.

9. Nasheralahkami, S., Golovashchenko, S., Pan, K., Brown, L. et al., "Characterization of Trimmed Edge of Advanced High

Strength Steel," SAE Paper 2016-01-0358, 2016, doi:10.4271/2016-01-0358


For More Information

Raj Sohmshetty

Ford Motor Company

313.317.9035

[email protected]

Sergey Golovashchenko

Oakland University

248.370.4051

[email protected]

Evolution of Die Wear and Sheared Edge Parameters …/media/Files/Autosteel/Great...Effects of Tool...

Documents

Transcript of Evolution of Die Wear and Sheared Edge Parameters …/media/Files/Autosteel/Great...Effects of Tool...