**4. Durability assessment considering residual stress**

The residual stress results derived from the above simulation are high as the yield stress of the cylinder block and the bushing, so the residual stress was used as the mean stress before the cylinder block was used for accurate durability assessment. Unlike the above situation, when the residual stress is low, there are few reasons to consider it. This is because, as shown in **Figure 18**, there is no difference in the durability assessment result according to the load size when the residual stress is low. In conclusion, the cylinder block, which is the subject of this study, has

**Figure 18.** *Mean stress influence on HAIGH diagram.*

### *Durability Assessment Considering Residual Stress DOI: http://dx.doi.org/10.5772/intechopen.90298*

The resulting equation assumes axial symmetry and does not take into account shear stress inherently. In addition, the constant surface pressure in the longitudinal direction is calculated, so it is not suitable for the shape of the cylinder block which is the object of this study, but it is judged to be suitable as the relative standard of

The residual stress of the derived cylinder block using the structural simulation is shown in **Figure 15**. In order to determine the suitability of the simulation results, the surface pressure of the bushing was confirmed by angle. The surface pressure distribution of the simulation results follows the general shape [7] of the Hertz contact theory and most of the length of the surface pressure is higher than the constant value derived from the numerical formula (Eq. 5). The reason is that the shape of the cylinder block is not perfectly symmetrical and shear stress is gener-

In addition, the shape and numerical value of the residual stresses were checked within the range of possible shrink fit to confirm the aspect of the change in the residual stress with respect to the rate of shrink fit [8]. As a result, as shown in **Figure 17**, the shape of the residual stress was less dependent on the rate of shrink fit, and the numerical value of the residual stress was almost linearly related to the rate of shrink fit. Therefore, it was possible to set the rate of shrink fit and the residual stress in a linear relationship within the range of the producible shrink fit. In this study, it was possible to select the rate of shrink fit optimized for the use environment by using this relationship. If the relationship between the rate of shrink fit and the residual stress was nonlinear, then the simulation was additionally performed to find

The residual stress results derived from the above simulation are high as the yield stress of the cylinder block and the bushing, so the residual stress was used as the mean stress before the cylinder block was used for accurate durability assessment. Unlike the above situation, when the residual stress is low, there are few reasons to consider it. This is because, as shown in **Figure 18**, there is no difference in the durability assessment result according to the load size when the residual stress is low. In conclusion, the cylinder block, which is the subject of this study, has

the surface pressure to be derived from the structure simulation.

*New Challenges in Residual Stress Measurements and Evaluation*

out the sections having linear relationship to find the optimal design.

**4. Durability assessment considering residual stress**

**Figure 18.**

**136**

*Mean stress influence on HAIGH diagram.*

**3.4 Estimate residual stress using simulation**

ated almost everywhere (**Figures 16** and **23**).

a high residual stress value. Therefore, in this study, the durability assessment was performed considering the residual stress. In addition, in this section, realistic load and boundary conditions considering the use environment are examined to improve the reliability of the structural simulation results.
