**2.2 Stage II**

In this stage, the investigation will focus on the analysis of residual stresses evolved in I-4 and V-6 engine blocks following different types of heat treatments

**Figure 4.** *Sketch illustrating cutting directions.*

*Generation and Relaxation of Residual Stresses in Automotive Cylinder Blocks DOI: http://dx.doi.org/10.5772/intechopen.93664*

**Figure 5.** *I-4 engine block.*

(solutionizing as well as artificial aging). The liners used in these blocks were preheated to 400°C using induction coils, prior to being inserted into the mold to promote a more uniform microstructure (**Figure 5**) [16].

The engine blocks followed solution heat treatment (SHT) at 500°C for 8 hours, then quenching/cooling in different media, prior to T6 and T7 aging treatment for various aging times. Two quenching media were applied: cold water, warm water. Artificial aging, T6 aging is carried out at for 10, 50 and 100 hours 170°C (T6 aging). As for T7 treatment, samples were aged at 250°C for 10, 50, and 100 hours aging times. The T7 treatment is used industrially. To facilitate the handling of the engine block in the foundry, the I4 engine blocks were cut in half. This procedure was carried out after validating that there would be no change in results between the whole block (four cylinders) and half the block (two cylinders).

The sectioning method is a complete destructive test and can be considered as the first proposed method for measuring residual stresses. It involves cutting of the component with an electric strain gauge attached, and relies on the measurement of local strain (using strain gages) induced due to the release of residual stress upon removal of material from the specimen [14–16].
