### CHAPTER 3: METHODOLOGY

3.1 Introduction

In this chapter, a research methods and procedures are discussed in order to conduct a simulation on fatigue analysis of aluminium alloy wheel under different load. The selection of the material is considered in the simulation to determine the mechanical properties of the material. It also includes general mathematical equation to calculate the fatigue life of the aluminium alloy wheel.

3.2 Description of Flow chart

The analysis flowchart was started by designing a three-dimensional model of wheel and applying the material of 6061-T6 aluminium alloy for the specimen by using Solidworks software. Aluminium alloy wheel specimen was created by using Solidworks software 2018 and then, the model was saved as by using IGES format. Next, the aluminium alloy wheel model was imported into Ansys software to conduct fatigue life simulation in order to obtain correct data result. In the simulation of fatigue life, there are several stages required for simulation. Static structural analysis setup is used in analysis system for fatigue life test. Input data on specifications of aluminium alloy was assigned first in Ansys engineering data. Then, meshing process was done on the model. The fixed support and the force are applied on the wheel rim model to run fatigue life test under static structural. The analysis of fatigue simulation will find out the fatigue properties such as the life, safety factor and damage of aluminium alloy wheel by using S-N curve graph. The results of the simulation data are imported into Microsoft Excel in order to make data comparison with the result of the previous researcher. In addition, the data obtained from Ansys software is validated by applying Basquin equation for calculation method in this research. The details of the flowchart for this analysis is shown in Figure 3.1.

### Figure 3.1: Flow chart

3.3 General Mathematical Equation

3.3.1 Basquin Equation

(3.1)

## Where:

By using the Basquin equation, the theoretical value of each number of cycles for aluminium alloy wheel was calculated. The calculated result for alternate stress amplitude by using Basquin equation should not be much different from the simulation result. Besides that, analytical calculation for Basquin is more convenient and useful for validating simulation data to ensure accuracy and acceptability of this research.

3.3.2 Percentage Error for Experimental and Theoretical

(3.2)

(3.3)

It is very important to justify the experimental and simulation data results. This is to ensure that the difference gap of percentage error in the graph is less than 10% between both S-N curves. The difference gap of percentage error for simulation and the theoretical (Basquin) also should be the same as equation 3.2 above.

3.3.3 Difference Gap Percentage Error

(3.4)

Difference gap percentage error for both Equation 3.2 and Equation 3.3 should be less than 10% in this research. For Equation 3.2, average percentage error is calculated between two data results which is experimental and simulation data. The simulation data is got from the Ansys software which have been plotted in S-N graph while the experimental data is obtained from the result of the previous researcher. While for Equation 3.3, some of the data results obtained from the simulation will be used to calculate theoretical data. The average percentage error between simulation and theoretical (Basquin) data will be recorded. Further details about theoretical (Basquin) calculation had discussed in Chapter 4.

3.4 Three-Dimensional Model Preparation

3.4.1 Solidworks 2018 Software

Solidworks 2018 software is used in this research to create a three-dimensional wheel model. Based on functional and manufacturing criteria, Solidworks 2018 software automatically generate the optimal shape of 3D modelling. Moreover, information about the material used for the wheel such as the mechanical properties of aluminium alloys can be easily found in this software. Furthermore, compared to the old Solidworks version, Solidworks 2018 software is easier and better upgraded from the material requirement perspective.

3.4.2 Model of the Wheel Rim

Figure 3.2 below shows the design of the wheel rim model for this research. The model specification used is a standard size of automobile wheel rim. The details drawing for the design is shown in Figure 3.3.

### Figure 3.2: Wheel Rim Model

Figure 3.3: Wheel Rim Model Schematic Diagram (millimetre unit)

3.4.3 Selection of the Material

The material selected for the 3D modelling of the wheel rim is 6061-T6 aluminium alloy, where the mechanical properties of the material identified in the literature review are indicated by (Suresh et al., 2018) as shown in Table 3.1 below. Before running the fatigue life simulation in the Ansys software, mechanical properties of the material must be correctly assigned to ensure the validation results are obtained.

Table 3.1: Mechanical Properties of 6061-T6 Aluminium Alloy (Suresh et al., 2018)

3.5 Simulation Procedures in Ansys Software

Ansys software is used in this research to run simulation of fatigue life on aluminium alloy wheel model. Ansys software can be used to create simulation that test the durability of the model, fluid movements and many more. By using Ansys software, a prediction method for the fatigue life of the wheel also can be applied to estimate the fatigue life of the wheel rim model. Moreover, the data about fatigue life, strength and crack propagation also can be easily found in Ansys software. In addition, Ansys software is more efficient and much easy to conduct compared to other software.

3.5.1 Analysis Setup of Fatigue Test

In Ansys software, static structural analysis system is used for fatigue life simulation. Therefore, a static structural analysis system was setup for the simulation in the software as shown in Figure 3.4 below. In addition, the static structural analysis system is integrated with engineering data, geometry, model, setup, solution and results for analysis setup.

### Figure 3.4: Static Structural Setup

3.5.2 Model Setup in Ansys Software

Before starting the simulation of the fatigue analysis, the model of aluminium alloy wheel rim is imported from Solidworks into Ansys software. Then, the input data on specifications of 6061-T6 aluminium alloy was assigned in engineering data to verify the material used. Figure 3.5 shows the import model with 6061-T6 aluminium alloy material assigned.

Figure 3.5: Import model with 6061-T6 aluminium alloy material assigned

3.5.3 Meshing Model Setup

The geometry selection is applied on the wheel rim model to define the body sizing under the mesh setup. Before generating the mesh, the element size was firstly assigned to determine the mesh size element of the model. In order to obtain efficient and accurate data, meshing process had done on the wheel rim model as shown in Figure 3.6 below.

### Figure 3.6: Model meshing

3.5.4 Boundary Conditions Setup

3.5.4.1 Force Applied

There are two parts of boundary conditions that is applied on the wheel rim model for fatigue life simulation which is force and fixed support. Force is applied on the aluminium alloy rim lip barrel. In order to determine the force applied, the ultimate tensile strength for the material which is 310 MPa is considered in this simulation. The first force applied on the model is 90% from the ultimate tensile strength follow with 80%, 70%, 60%, 50%, 40% and 30% of ultimate tensile strength.

Figure 3.7: Force applied on the model (red area)

3.5.4.2 Fixed Support Applied

For the fixed support, this boundary condition should be applied on the wheel rim model. The fix support is applied on each wheel lug holes to make sure the body or part is fixed so that when the load is applied to that body it does not move. The body also will remain rigid (stiff) without any deformation. Figure 3.8 shows the steps of fixed support applied on the wheel rim model.

Figure 3.8: Fixed Support applied on the model (purple area)

The fatigue life simulation is continued with different load which is for 80%, 70%, 60%, 50%, 40% and 30% of ultimate tensile strength. The steps to apply boundary conditions is the same as shown in Figure 3.7 and Figure 3.8 above. From the simulation, the S-N curve graph will automatically be generated, and the number of alternating stress and life cycles obtained will be shown in the graph.

3.5.5 Solution Setup

As shown in Figure 3.9 below, the fatigue analysis setup is displayed under the solution in the fatigue tool. All the information such as the type of loading, analysis type and stress component will be inserted in the fatigue tool.

### Table 3.2: Fatigue Analysis Setup

## Criteria Input

Type of Loading Constant Amplitude Load

## Loading Ratio 0.1

## Mean Stress None

### Analysis Type Stress Analysis

Figure 3.9: Constant Amplitude Load and Mean Stress Correction Theory for Loading Ratio, R=0.01

3.5.6 Expected Results

The alternating stress result of the wheel will be displayed in Ansys software. The minimum until maximum values of alternating stress is found for the model after fatigue life simulation process. The red contour indicates maximum equivalent alternating stress while the blue contour indicates minimum equivalent alternating stress of the model.

The Ansys software will indicate the life cycle result of 6061-T6 aluminium alloy wheel model. The results will be showed that the lowest life cycle will display red contour which is the possible failure area of the model. The high life cycles region will display blue contour which means the strongest area of the model.

3.6 Parametric Study Solution Display

The Ansys software will display the table of properties obtained from the simulation. All data were exported into Microsoft Excel for further details of analysis and calculation.

Table 3.3: Table of result from Ansys Software

No Percentage (%) Load (KN) Number of Cycle Alternating stress (MPa):

## Simulation

1 90% 279

2 80% 248

3 70% 217

4 60% 186

5 50% 155

6 40% 124

7 30% 93

Table 3.4: Comparison data between both Simulation and Experimental

No Number of Cycle Alternating stress (MPa):

### Simulation Alternating stress (MPa):

### Experimental Error (%)

1

2

3

4

5

6

7

## Average Error

Table 3.5: Comparison data between both Simulation and Theoretical (Basquin)

No Number of Cycle Alternating stress (MPa):

### Simulation Alternating stress (MPa):

### Theoretical (Basquin) Error (%)

1

2

3

4

5

6

7

## Average Error

3.7 Resources Planning

All the resources used in this research was listed in Table 3.6 below. The total cost required to complete this research was RM 0 due to all items is free of charge. All of the resources can be found in the internet for free version and it does not require any cost to download the software.