SMC 4133 AUTOMOTIVE STRUCTURES MATERIAL SELECTION This section demonstrates a method for preliminary selection of materials Steel is the most common material for the contemporary body structure Mild steel was the predominant steel grade used in the past due to its favorable balance of strength, formability & cost In recent years, strict safety standards has made steel application extended to higher-strength grades Increase the strength may also increase the cost Another significant parameter is material elongation; increased strength comes at a reduced elongation at failure All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.

SMC 4133 AUTOMOTIVE STRUCTURES MATERIAL SELECTION Preliminary selection of materials can be made by the following steps: Determine the primary function of the structural element: stiffness, strength, & vibration 2. Determine the objective of material selection: minimize mass etc. 3. Derive the material index corresponding to the type of structure, the function, the objective and constrained dimensions 4. Rank materials by descending material index using a tabular form or graphic 5. Make the final material selection after gathering information All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.

MATERIAL SELECTION Example 1 SMC 4133 AUTOMOTIVE STRUCTURES MATERIAL SELECTION Example 1 Design requirements based on allowable deflection, delta = 20mm and applied load, F = 6680N Optimized beam thickness Optimized beam mass Minimum cost Constraints: Section width = 40mm, height = 80mm, length = 1000mm All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.

MATERIAL SELECTION Solution SMC 4133 AUTOMOTIVE STRUCTURES MATERIAL SELECTION Solution Design requirements based on allowable deflection, delta = 20mm and applied load, F = 6680N Optimized beam thicknessMS Optimized beam mass CFRP Minimum cost MS Constraints: Section width = 40mm, height = 80mm, length = 1000mm material E A t, m rho M, kg $/kg Cost, $ steel 2.00E+11 -6.68E-06 4.30E-03 7860 7.53 0.80 6.02 AHSS 1.00 alu 7.00E+10 -1.91E-05 9.40E-03 2710 5.16 2.80 14.44 smc 1.00E+10 -1.34E-04 2.80E-02 2000 7.17 6.00 43.01 mg 4.50E+10 -2.97E-05 1.20E-02 1830 4.22 4.80 20.24 ti 1.20E+11 -1.11E-05 6.50E-03 4430 6.16 100.00 616.21 gfrp 2.50E+10 -5.34E-05 1.74E-02 1850 5.49 20.00 109.70 cfrp 1.60E+11 -8.35E-06 5.20E-03 1600 1.82 40.00 72.95 All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.

SMC 4133 AUTOMOTIVE STRUCTURES MASS ESTIMATION This section presents a mean to generate initial mass estimations Mass of vehicle subsystems is crucial in determining structural requirements For a new vehicle design, there are no existing subsystems to weight. Thus, it is critical to have a method to estimate initial mass of the subsystems Regression-based mass estimation - to arrive at an estimate for the curb (with fluids) and gross (passenger, cargo, and option) vehicle mass and each of the subsystems All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.

MASS ESTIMATION Example 2 SMC 4133 AUTOMOTIVE STRUCTURES MASS ESTIMATION Example 2 A new vehicle is in the planning stage. It is targeted at 5 passengers with a 120kg cargo capacity. The vehicle length is 4.7m and 1.8m width. The test weight for fuel economy is 1480 kg resulting in a 1341 kg curb mass. Determine the curb mass for an average vehicle and to compare it to the target test weight and mass for each subsystem. Solution: Mcurb =171 x 4.7 x 1.8 = 1446.6 kg Mdiff = 1446.6 – 1341 = 105.7 kg All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.

MASS ESTIMATION Mass-compounding model SMC 4133 AUTOMOTIVE STRUCTURES MASS ESTIMATION Mass-compounding model Unplanned mass increase in a component during vehicle design has a uncertain effect throughout the vehicle. Other components need to be resizedmay increase vehicle mass even more A reduction of mass in a component by a new technology can result in an even more mass reduction (secondary mass reduction) for overall vehicle Mass-compounding model is a way to quantify the secondary mass change. Each subsystem has a mass influence coefficient-as vehicle mass changes the subsystem may also be resized. All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.

MASS ESTIMATION Mass-compounding model SMC 4133 AUTOMOTIVE STRUCTURES MASS ESTIMATION Mass-compounding model The resulting mass for subsystem: Ratio method All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.

MASS ESTIMATION Mass-compounding model Example 3 SMC 4133 AUTOMOTIVE STRUCTURES MASS ESTIMATION Mass-compounding model Example 3 From example 2 & using mass-compounding model, estimates mass reduction in a vehicle considering 5 hypothetical technologies. Solution: 1446.6 – 40 – 40(1.079) = 1363.4 kg Mdiff = 1363.4 – 1341 = 22.4 kg All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.

MASS ESTIMATION Mass-compounding model Example 3: Solution SMC 4133 AUTOMOTIVE STRUCTURES MASS ESTIMATION Mass-compounding model Example 3: Solution From example 2 & using mass-compounding model, estimates mass reduction in a vehicle considering 5 hypothetical technologies. All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.