electromagnetic shearing of ultra high strength steels

Electromagnetic Shearing of Ultra High Strength Steels

PIs: Brad Kinsey, UNHJyhwen Wang, TAMU

Executive Summary:

• Objective/Industrial Need: effective shearing of UHSS (>1 GPa)

• Approach: electromagnetic shearing with durable coil fabrication

• Deliverables: assessment of shear edge condition and coil life

• Budget and Timeline: $150k for 1.5 years; supports one RA

• Comments: close collaboration with Bmax on project for experiments; integrates with additional project on “Prediction of trimmed edge stretching performance”

NSF I/UCRC Planning Meeting Slide 2

10. Electromagnetic Shearing of Ultra High Strength Steels

Industrial Need and Relevance:

• Shearing of UHSS components in a manner that will not cause downstream failures, e.g., edge cracking, is challenging.

• Electromagnetic (EM) shearing is dominated by bending/compression deformation versus shear fracture in conventional shearing.

• While EM shearing is a promising alternative, coil life and strength are concerns.



Conventional shearing

Electromagnetic shearing

Uhlmann and Scholz, 2003, Dortmund Colloquium


Project Objectives:

• Effectively shear UHSS (> 1 GPa)

• Characterize shear edge condition through microstructural analyses

• Extend EM coil strength and life so can be effectively implemented in a production environment


Combined forming and shearing operation


Approach/Methodologies:• To create more a durable EM coil, take

advantage of electromagnetics in process.

• Electrical energy is only concentrated on the outer edge of the coil cross-section in the skin depth area. Thus, this is the only location in the cross-section where the highly conductive, lower strength material is required.

• Credit for this idea is given to Erman Tekkaya’s group at TU-Dortmund, Germany.


Failure of insulator material

Failure of coil material

Golovashchenko, JMEP, 2007


Approach/Methodologies:

• Skin depth calculated from:

• Typical values ~1-1.5 mm


𝛿 = 2𝜌

𝜇0𝜇𝑟𝜔

ρ = Electrical resistivity of coil materialµr = Permeability of coil materialµ0 = Permeability of free space (4π×10−7 N/A2)ω = Angular frequency of the circuit (e.g., ω=8.1x104 rad⁄s)

Normalized current densities

Steel base

Outer Cu layer

• Electroplating will be used to create thin Cu layer on outer edge of steel EM coil


Approach/Methodologies:

• Once coil is fabricated, both conventional (for comparison) and EM shearing experiments will be conducted.


Kamal and Daehn, JMSE, 2007

Coil with leads to capacitor back

Coil embedded in epoxy

Thibaudeau, MS Thesis 2011


Deliverables:

• Assessment of shear edge condition from both EM and conventional processes

• Plated, durable electromagnetic coil

• Analyses of coil strength and life

• Criteria and empirical guidelines for process implementation


Thibaudeau, MS Thesis 2011


Budget and Timeline:

Estimated cost of the project is $150k for 1.5 year.

Includes RA support, costs for coil fabrication, and testing


Task / MilestoneYear 1 Year 2

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

Fabricate coil

EM shearing & coil life testing

Conventional shearing tests

Shear edge characterization


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?


electromagnetic shearing of ultra high strength steels

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