smdi lightweight twist beam development/media/files/autosteel/great designs in steel... · w w w ....

w w w . a u t o s t e e l . o r g

SMDI LIGHTWEIGHT TWIST BEAM DEVELOPMENT

Scott Keefer

Multimatic Engineering


Acknowledgements

OEM Project Team:

Doug Howe

Ford Motor Company

Ranvir Singh Jalf

Chrysler Group LLC

William Pinch

General Motors Company

Cory Taulbert

General Motors Company

Multimatic Engineering Team:

Nik Balaram

Tudor Boiangiu

Pardeep Dhillon

Eric Gillund

Bob Howell

Scott Keefer

Paul Saadetian

Murray White

Steel Project Team:

David Anderson

Steel Market Development Institute

Jon Fleck

AK Steel Corporation

Tom Wormold

ArcelorMittal USA LLC

Dean Kanelos

Nucor Corporation

Srinivasan Laxman

Severstal North America

Jon Powers

Severstal North America

Paul McKune

ThyssenKrupp Steel USA, LLC

Bart DePompolo

United States Steel Corporation


Agenda

• Objective and Scope

• Design Targets

• Development Process

• Design Proposals

• Performance

• Mass

• Manufacturing

• Cost

• Summary and Conclusions


Objective and Scope

• The objective of this project was to develop a lightweight

steel proof-of-concept* twist beam design that achieves

a 15 to 25% mass reduction with equivalent structural

and elasto-kinematic performance relative to the

baseline design at a ≤ 10% cost premium.

• The baseline design for package, performance, and

mass is a current production original equipment

manufacturer (OEM) twist beam assembly

• Project timing: 26 weeks

*Designs are subjected to “typical” OEM requirements;

specific OEM production requirements may require further development and validation

OEM Baseline Twist

Beam assembly


Structural

Performance Equal to, or exceed the baseline Mass

15-25% lower than the

baseline Cost ≤10% cost

increase over

the baseline

Package Meet available packaging

constraints

Corrosion Meet OEM corrosion

requirements

Design Targets

OEM Baseline Twist Beam


Structural Performance

Extreme Loads

Set ≤ 1.0 mm

Elasto-Kinematic

Performance (Kinematics

and Compliance)

Match baseline

performance

Durability

Life ≥ 1.0

Requirements


Development Process

4. Cost Assessment

1. Concept Development - Size / Shape Optimization (stiffness/strength)

•Kinematics and Compliance Behavior

3. Manufacturing and Corrosion

Iteration

2. Design Development

S-Beam Concept

U-Beam Concept

• Component Mass Optimization

• Durability

• Strength


Concept Development

• An iterative topology optimization process was used in consideration of

stiffness and strength for the given design space of the twist beam

• The optimization program resulted in two candidate designs for further

development: the “U-Beam” and the “S-Beam”

• More than 100 studies were completed, investigating the influence of:

– A) Stress Limits (no limit, 400 MPa, 300 MPa, 200 MPa);

– B) Manufacturing Constraints (draw, stamp, extrusion);

– C) Package Space / Biasing (design space restrictions);

– D) Algorithm Parameters (varied objectives, constraints); and

– E) Model Setup (bushings, constraints, load cases).

• Software used for analysis:

Pre-Processor Solver Post-Processor

HyperMesh 11 OptiStruct 11 HyperView 11


Concept Development


Concept Development: U-Beam

Final U-Beam Concept


U-Beam Design

Design:

•Tubular transverse and swept longitudinal members, 22MnB5

material, 2.5 mm thick

•Transverse member with inverted “U” cross section and 20%

increased OD near centerline

•Added “bulkheads” to stabilize the transition area

•DP780 trailing arms, 1.8 mm thick

•Aggressive gauge reductions with AHSS and UHSS

1.90mm Air

Gap

All components MIG welded


Baseline Design

Design:

•Tubular transverse member with

inverted “V” cross section, high

strength FB590 material, 3.2 mm

thick

•Tubular trailing arms, HSLA, 5.0

mm thick


Performance and Mass

• Finite element analysis (FEA)

methods were used to predict the

structural performance

• An iterative optimization strategy

was used to minimize the mass of

each design while meeting the

specified structural requirements

– Durability

– Extreme loads (permanent set)

– Kinematics and Compliance

behavior


Materials

Engineering Stress-Strain Comparison


HAZ – Materials

Material modeling considerations

• Material fatigue property reductions

of 20% in the weld Heat Affected

Zone (HAZ) for all high-strength (HSS),

advanced high-strength (AHSS) and

ultra high-strength steel (UHSS)

grades, per SMDI modeling guidelines

(durability load cases only)

• 20% material strength reduction in

HAZ zone for UHSS grades with

ultimate strengths greater than

800MPa (strength load cases only) HAZ elements in

weld areas


HAZ – Durability Implementation

The ‘80% HAZ’ properties applies to all steels including

UHSS, AHSS and HSLA.

Beam

(2.50mm)

22MnB5

Spring Seat

(2.50mm)

SPFH 540

Trailing Arm

(1.8 mm)

DP780

Trailing Arm HAZ

(1.80mm)

80% of DP780

Beam HAZ

(2.50mm)

80% of

22MnB5

Spring Seat HAZ

(2.50mm)

80% of SPFH 540


HAZ – Strength Implementation

The ‘80% HAZ’ properties applies to UHSS only.

Beam

(2.50mm)

22MnB5

Spring Seat

(2.50mm)

SPFH 540

Trailing Arm

(1.80 mm)

DP780

Trailing Arm HAZ

(1.80mm)

DP780

Beam HAZ

(2.50mm)

80% of

22MnB5

Spring Seat HAZ

(2.50mm)

SPFH 540

Note: Shell welds

themselves are assigned

properties corresponding

to the lower strength

material of the two

joining components. The

shell weld thickness is

determined by a

weighted average

between the two

component thicknesses.


U-Beam Design – Materials

Beam

(2.50mm)

22MnB5

Spring Seat

(1.50mm)

SPFH 540

Damper Bracket

(1.50mm)

SAE 550X

Bushing Sleeve

(2.00mm)

DOM Steel w/

550MPa yield Spindle Sleeves

(3.00mm stepped

to 8.00mm)

SAE 4130 Q&T Trailing Arm Bracket

(1.80mm)

DP-780

Damper Plate

(1.50mm)

SAE 550X Bulkhead

(1.50mm)

SAE 550X

Damper Sleeve

(5.00mm)

SAE 4130 Q&T


Requirement

≥ 1.0*

Durability Analysis Results

Results are presented for the (3) most severe load cases

Most severe

(Higher is Better)

*See Final Report: Lightweight Twist Beam Development for further

discussion of durability targets


OEM Baseline - Max Twist Event

Worst Case Condition

Max Twist Load Case

Contoured to the target minimum of 1.0 life

Minimum Life

Durability Assessment


Worst Case Condition

Max Twist Load Case U-Beam - Max Twist Event

Contoured to the target minimum of 1.0 life

Minimum Life

Durability Assessment


Requirement

< 1.0

Most

severe

Extreme Load Cases

Results are presented for the (3) most severe load cases

(Lower is Better)


Plotted to a maximum of

1% to show areas

undergoing deformation

Plastic strain

Strength Assessment

OEM Baseline – Max Vertical Event (LHS)


Strength Assessment

U-Beam - Max Vertical Event (LHS)

Plotted to a maximum of

1% to show areas

undergoing deformation

Plastic strain


Design OEM Baseline Design U-Beam S-Beam

Image

Trial Tr3 Tr539 Tr784

Extreme Load / Permanent Set (nonlinear material & geometry)

Load Case NameMax target

(mm)Set / target Set / target Set / target

Max Vertical Event 1.0 1.00 0.52 0.01

Max Forward event 1.0 0.22 0.14 0.00

Max Aft Event 1.0 0.08 0.53 0.00

Durability Analysis

Load eventTarget

(1 life)Life / Target Life / Target Life / Target

LHS/RHS Bump Event 1.0 1.0 1.5 17.3

Max Twist Event 0.18* 1.0 4.3 3.7

Max Cornering Event 1.0 1.0 1.0 5.8

* 0.18 life target established based on OEM prediction and concurrence for this load case

Structural Performance Summary

Primary

Design Drivers

Secondary


Mass Summary – Beam Assembly

-14.9%

-30.0%


Mass Summary – Beam Structure

-16.3% -32.8%


Elasto-Kinematics

A correlated ADAMS model of the OEM baseline twist beam

was created. This model was used for comparisons to the

proposed designs.

• Flex bodies for the baseline twist beam were generated

based on mesh created for structural analysis.

• The ADAMS model was updated with the following

information provided by the OEM:

– Spring rate / spring preload at design position (curb)

– Jounce / rebound bumper stiffness

– Bushing stiffnesses

– Tire stiffness

– Tire unloaded radius


Elasto-Kinematics

Key steps in correlating the OEM baseline ADAMS model:

• The flex bodies were correlated with the Abaqus model

• Bushing stiffnesses as installed in the twist beam were

characterized at Multimatic via testing

• ADAMS predicted responses were compared to measured

Kinematics and Compliance (K&C) vehicle data


Elasto-Kinematics

• During the twist beam development program, K&C

assessments were performed and the designs tuned to

match the OEM baseline K&C characteristics, thereby

providing confidence that the on-road vehicle ride and

handling behavior of the two beam designs would be very

similar.

• A full set of K&C plots is included in the SMDI Final Report:

Lightweight Twist Beam Development

Roll - Roll Steer Roll - Roll Steer FRONT LEFT FRONT RIGHT

<--left steer angle [deg] right--> <--left steer angle [deg] right-->

Roll - Roll Steer REAR LEFT _REAR RIGHT

<--left steer angle [deg] right--> <--left steer angle [deg] right-->

<--

right tu

rn B

ody R

oll

Angle

[deg] left turn

-->

<--

right tu

rn B

ody R

oll

Angle

[deg] left turn

-->

<--

right tu

rn B

ody R

oll

Angle

[deg] left turn

-->

<--

right tu

rn B

ody R

oll

Angle

[deg] left turn

-->

-4.50

-3.00

-1.50

0.00

1.50

3.00

4.50

-0.20 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15 0.20

ADAMS :: OEM Baseline ADAMS :: Trial 539 U Beam

-4.50

-3.00

-1.50

0.00

1.50

3.00

4.50

-0.20 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15 0.20

ADAMS :: OEM Baseline ADAMS :: Trial 539 U Beam

-4.50

-3.00

-1.50

0.00

1.50

3.00

4.50

-0.20 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15 0.20

ADAMS :: OEM Baseline

ADAMS :: Trial 539 U Beam

-4.50

-3.00

-1.50

0.00

1.50

3.00

4.50

-0.20 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15 0.20

ADAMS :: OEM Baseline

ADAMS :: Trial 539 U Beam


U-Beam Design – Manufacturing

• Considerations

– Mn22B5 main tube forming

feasibility

– Bulkhead assembly

– Mn22B5 tubular ends forming

feasibility

– Stampings

– Weld Access

– Coating

Expert Manufacturing

Assessment via Multimatic

and partner Linde+Wiemann


1

2

3

4 5

6

U-Beam Design – Manufacturing

• Considerations

1. Mn22B5 main tube forming feasibility • Increased OD near centerline via ACCRA® process or purchased variable OD

tube

• Hot-formed “U” cross section judged feasible

2. Bulkhead assembly • Feasible with added shoulder form to self-center and locate the bulkhead to the

center tube

3. Mn22B5 tubular ends forming feasibility • 90°bend and end shape judged feasible

4. Stampings • Conventional – judged feasible

5. Weld Access • Feasible (weld length = 5980 mm)

6. Coating • Zinc-nickel coating judged

feasible (current production technology)


Corrosion

• To maintain OEM corrosion requirements, corrosion

protection is generally applied to components based on

material gage

• Sheet steel material gage limit (OEM specific):

– > ~2.0mm: E-coat finish

– < ~2.0mm: Hot dipped galvanized coating* + E-coat

• For a complex welded assembly such as a twist beam

containing component gages <2.0mm, a standard welding

process can be maintained with the use of uncoated

materials and zinc-nickel plating of the assembly followed

by E-coat

*OEM specific, e.g. Hot Dip G60 / G60 (GI) or Hot Dip Galvanneal A-40 (GA)


Corrosion

• Additionally, the project included consulting with the

Auto/Steel Partnership Lightweight Chassis Corrosion

project team on corrosion countermeasures for the beam

designs. This team is conducting a build and test program

to gather data on the corrosion performance of AHSS and

UHSS with various treatments. Possible approaches

include:

– Powder coating weld areas

– Mild alloying of materials via added copper or chrome

– Post-formed coatings, especially for hot stamped boron

steels


Cost

• Twist beam assembly

(structure and bushings)

– OEM baseline

– U-Beam (selected

alternative)

• Cost of manufacture and

bushing assembly

– 30k, 100k and 250k

vehicles per year

– Six-year program

Baseline: Includes E-Coat

U-Beam: Includes zinc-nickel

plating of the asy & E-coat


Cost Summary


Cost Summary

Cost relative to OEM Baseline up to 250,000 volume

12%

15% 15%


Summary

• Two steel twist beam designs were developed to determine the lightest design which met or exceeded the structural and elasto-kinematic performance of the OEM baseline design. The U-Beam design was chosen as the preferred alternative due to its superior structural, elasto-kinematic, and mass performance.

• Manufacturing costs were estimated for the baseline and selected U-Beam designs

• U-Beam Design

– 22MnB5 tube

– DP780 sheet

– SPFH540 sheet


Conclusions

• U-Beam Design: The selected U-Beam

design provides maximum mass

reduction of 7.5 kg (30.0%) relative to

the OEM baseline assembly and

meets all structural and elasto-

kinematic requirements

– 12 to 15% cost premium relative to

the OEM baseline at a production

volumes of 30k vehicles / year to

250k vehicles / year

– Deemed production feasible based

on expert manufacturing

assessments

smdi lightweight twist beam development/media/files/autosteel/great designs in steel... · w w w ....

Documents