**3. Methods for durability assessment of cylinder block**

In general, standard, measurement, experiment and simulation can be considered as methods for durability assessment. The above methods will be described with respect to the cylinder block in which the residual stress is present.

In the case of the standard, the reliability of the evaluation result can be secured based on the authority of the standard, but the accuracy of the product with complicated shape is degraded in order to guarantee the performance. The reason is that the standard contains some assumptions and simplifications in the formulas for general use.

In case of measurement, there is an advantage that it can confirm the accurate state in real time when using, but there is a disadvantage that it is only possible to check the local state instead of the total state. In addition, there are many difficulties in measuring a cylinder block having a relatively small size as well as a rotating body. Also, there is a risk that the location of the high stressed portion, which is an evidence for durability safety, should be selected only by experience.

Experiments provide a relatively complete assessment of the product as a whole, but it takes time and expense to derive the results of the experiment. Especially, the improvement process and the short processing period, which are often derived when the product development stage is the basic design, make the experiment only used in the final product development stage. These characteristics make the experimental method difficult to use for the purpose of this study (predicting the residual stress and evaluating the durability thereof), which is the working area of the basic design.

Finally, in the case of simulation, the overall evaluation of the product is possible and it is possible to respond quickly to the improvement. However, as shown **Figure 3**, unlike the measurement and the experiment, simulation is difficult to consider stochastic effect. Stochastic effects of products not confirmed by

**Figure 3.** *Deterministic and stochastic in evaluation method.*

**Figure 4.**

*Methods for engineering analysis.*

simulation methods are expected to be confirmed in the final tests performed prior to final product launch.

The simulation used in this study is structural simulation. The Finite Element Method (FEM) was used as shown in **Figure 4**). The finite element method is one of the powerful methods to numerically solve wide engineering problems. Solve the equation of the virtual works (Eq. (4)) using the equilibrium equations and boundary conditions equation (Eqs. (1)–(3)) in the engineering problem domain. Simulations use the weighted residual method as a way to solve this equation of virtual work linearly. By using this weighted residual method, it gives an approximate solution of the matrixed problem. At this time, since the method used to solve the matrixed problem is the node and the element, the know-how of element setting that does not distort the coordinate system of problem is important for solving the problem.

shrink fit suitable for the size and material of the cylinder block and copper bushing

The shape and material have a great influence on the residual stress as well as the

rate of shrink fit when the copper bushing is pressed into the cylinder block. In order to predict the accurate residual stress, a characteristic test was performed on the material except for the shape selected through the design [4]. The reason for this is that, in the case of metallic materials, the material properties such as yield stress and tensile stress vary depending on the production method of the material.

mentioned yield stress and tensile stress value should be basically confirmed. The test results of yield stress and tensile stress are shown in **Figure 7** and **Table 1**. Experimental results were derived from other common aspects that copper

Therefore, in order to perform accurate durability assessment, the above-

before use.

**Figure 7.**

**129**

*Material property test results.*

*Crack of cylinder block.*

**Figure 6.**

**3.2 Material property check**

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