Table 3: The effect of measurement method on the average fatigue threshold and fracture toughness of the austempered AISI 4140 steel alloy.
| Fatigue threshold (MPa√m) | Fracture toughness (MPa√m) | |
| Calculated from proposed method | 6.1 | 57.6 |
| Experimentally determined from conventional ASTM method | 5.5 +/- 2.9 | 62.4 +/- 6.6 |