|
Steel
vs. Aluminum: Mechanical Properties
| Grade |
Yield
Strength, as received
MPa - (ksi) |
Yield
Strength, on Vehicle
MPa - (ksi) |
Tensile
Strength
MPa - (ksi) |
%EL |
n-value |
R-value |
|
Steel
Grades |
| Mild
Steel |
170
(25) |
187
(27) |
300
(44) |
42 |
0.22 |
1.9 |
| Dr
210 |
220
(32) |
242
(35) |
360
(52) |
40 |
0.2 |
1.8 |
| BH210 |
220
(32) |
264
(38) |
360
(52) |
36 |
0.18 |
1.7 |
| BH250 |
260
(38) |
312
(45) |
384
(56) |
34 |
0.17 |
1.5 |
| HSLA340 |
360
(52) |
400
(58) |
440
(64) |
26 |
0.16 |
1.2 |
| DP600 |
360
(52) |
468
(68) |
610
(89) |
27 |
0.16 |
1 |
| TRIP |
400
(58) |
592
(86) |
610
(89) |
35 |
0.23 |
1 |
| DP780 |
400
(58) |
520
(76) |
790
(115) |
24 |
0.14 |
1 |
| DP980 |
560
(82) |
730
(106) |
990
(144) |
21 |
0.12 |
1 |
|
Aluminum
Grades |
| 5754-O |
90
(12) |
120
(16) |
205
(30) |
26 |
0.26 |
0.75 |
| 5182-O |
135
(20) |
150
(22) |
250
(36) |
28 |
0.3 |
0.79 |
| 6111-T4 |
165
(23) |
241
(35) |
295
(43) |
26 |
0.25 |
0.73 |
Note: These example properties are used only
for general design guidelines..
In order to achieve the most optimal weight by material thickness selection, a prospective design must utilize as many components of the on-car materials properties as possible in the early design stages. Fig. 1 indicates an example of these components for a DP 590Y grade taking into account the sheet strength, work hardening due to forming, bake hardening, and positive strain rate effects. Most steel grades currently utilized in production possess all of these components.
For the aluminum alloys, the 6XXX series is heat treatable, while the 5XXX class of alloys is not [I.J. Polmean, “Light Alloys – Metallurgy of the Light Metals”, Third Eddition, ISBN 0 340 63207 0]. There is often an absence of strain rate effects with aluminum (found to be slightly negative for 5754-O and approximately zero for 6111-T4), but they do possess a level of work hardening comparable to steel [McGuire and Wilson, 2001]..
Fig. 1. Components of on-car mechanical properties for Dual Phase 590Y (please note that these values will change depending on the exact application).
Based on these relationships, for example, the best option to improve dent resistance for outer panel surfaces or maximize the crush potential of a prospective material is to consider all of the property components. Weight savings for many structural members can also be realized by carefully balancing the maximum yield strength and formability in the early design stages. To accomplish this analysis most effectively, the material supplier must work closely with the automaker for each individual design application in order to derive the correct material property data, most representative of the intended design testing. An initial FEA formability analysis (one step or incremental) will give the necessary data for deriving such a curve that can then be used for further FEA structural evaluations, palm printing, weight/shape/stiffness optimization, and dent resistance simulations as examples.
This approach will allow for the most efficient use of material properties and yield the best strength-stiffness to weight ratio for the final intended design.
Back
|
Top
|
Next
|
