An Innovative High Strength Steel Engine Cradle Concept

Transcription

1 An Innovative High Strength Steel Engine Cradle Concept Michael Gulas Projects Manager - FEA Market Development & Product Applications Dofasco Inc. 1

2 Program Objectives Demonstrate weight savings achievable using AHSS in the design of an optimized engine cradle, with little or no cost penalty The optimized design will have significant weight savings, equivalent stiffness, and increased durability compared to a baseline (non-optimized) design The design uses 2004 design targets for a contemporary mid-sized sedan The optimized design uses advanced steel materials and manufacturing techniques that push the boundaries of conventional design 2

3 Baseline Steel Engine Cradle Limited package space Transverse V6 engine Mid-size sedan High Volume Materials are typical mild steels Front Body Mounts Engine Mount Transmission Mount Rear Body Mounts 32 kg Lower Control Arm Mounts 3

4 Baseline Cradle - Manufacturing Stampings Tubes Hydroformed Tube 4

5 Advanced Steel Engine Cradle Stiffness is a primary design consideration Galvanized AHSS grades chosen for durability and crash Packaging constraints and mounting locations maintained Front Body Mounts Engine Mount Transmission Mount Rear Body Mounts Lower Control Arm Mounts 5

6 Manufacturing Methods AHSS Bent Tube End Flared HSS Tube Bent Flat Strip Roll Formed UHSS Section Hydroformed HSS Tube AHSS Stampings Stamped Clam Shells 6

7 Advanced Steel Cradle Composition AHSS % HSS - 49% Mild Steel - 8.5% (by mass) 7

8 Hydroformed Tube Hydroformed, Hydropierced Tube 350/440 MPa HSS HR Steel Tube for Formability, Strength Tube - Ø 75mm X 2.15mm wall X 1500mm Weight kg 8

9 Engine Support Beam Roll Formed, Laser Cut Laser Welded Insert HSLA 120ksi (830MPa) HDG Steel - Ultra High Strength Steel for Durability Beam mm X 600mm Welded Insert mm X 500mm Weight kg 9

10 U-Tube Single Bent Tube, split for front tubes DP 340/600 AHSS HR Steel Tube for crash energy absorption Tube - Ø 75mm X 2.80mm wall X 750mm Weight kg 10

11 Front Tube Expanded (Flared) end tube for laser butt weld 350/440 MPa HSS HDG Steel Tube for formability, strength Tube - Ø 65mm X 0.65mm wall X 560mm Weight kg 11

12 Clam - Shell Style Stamped Parts Front Body Mounts - L & R Right and left opposite stampings HR Mild Steel Top mm thick sheet - Weight kg Bottom mm thick sheet - Weight kg Rear Left Body Mount Top - HR DP 600 AHSS Steel mm thick sheet - Weight kg Bottom - DP 600 AHSS HDG Steel mm thick sheet - Weight kg Rear Right Body Mount HR DP 600 AHSS Steel Top mm thick sheet - Weight kg Bottom mm thick sheet - Weight kg 12

13 Miscellaneous Stampings Front LCA Brackets HR DP 600 AHSS Steel Left mm thick sheet - Weight kg Right mm thick sheet - Weight kg Transmission Bracket Bent Plate HR DP 800 AHSS Steel 2.70 mm thick sheet Weight kg Rear LCA Brackets HR DP 600 AHSS Steel 3.0 mm thick sheet Weight kg Rack Mounts HR Steel 2.00 mm thick sheet Weight kg 13

14 Stiffness Comparison Baseline Cradle Max. Deflection mm Advanced Cradle Max. Deflection mm 14

15 Durability Comparison Comparison using Durability Safety Factor as a measure Durability Safety Factor defined as the UTS over peak stress The higher the Durability Safety Factor, the better the Durability Baseline Cradle Durability Safety Factor 4.75 Advanced Cradle Durability Safety Factor

16 Forming of Stamped Parts Safety Zone Low Strain Strong Wrinkle Tendency Wrinkling Tendency Safe Marginal Fail 16

17 Forming of Hydroformed Tube Tube Bending Hydroform Tube Crush 17

18 Results Weight: 37.5 % reduction Achieved Stiffness targets Improved Durability (higher strength steels) Potential for Improved Crashworthiness Comparable Cost (AHSS grades) 32 kg 20 kg 18

19 Summary This work took advantage of the synergies that can be achieved between HSS, AHSS and novel manufacturing methods to meet 2004 mid-sized sedan specifications Innovative all steel design incorporating: - AHSS (42.5%), HSS (49%) - Advanced manufacturing techniques such as: Hydroforming Roll Forming End Flaring Laser or MIG Welded joints Weight: 20 kg vs 32 kg Stiffness targets met or exceeded in all cases Durability improved in all cases 19

20 An Innovative High-Strength Steel Engine Cradle Concept Questions? 20