## 5 Methodology Used in This Study  
To examine the effect of journal bearing geometry on wear, a slider-crank mechanism featuring a journal bearing between the crank and connecting rod is analyzed. For reference, the mechanism outlined in [24] is used. In this configuration, both the crank and connecting rod are made from aluminum alloy (AL6061-T6). The crank has a length of 38.1 mm and a mass moment of inertia of 204 kg\(\cdot\)m\({}^{2}\), while the connecting rod is 101.6 mm long with a mass moment of inertia of 5500 kg\(\cdot\)m\({}^{2}\). The crank and connecting rod have respective masses of 404.5 g and 817.5 g.  
The slider includes an aluminum (AL6061-T6) bushing pillow block with an attached thrust air bushing, which is mounted on a dovetail air bearing stage to enable smooth sliding. The entire slider assembly has a total mass of 8500 g. Further details about this mechanism are available in [44]. A diagram of the mechanism is provided in Figure 3, and its properties are detailed in Table 1. A spring with a spring constant of 500 N/m is connected to the slider, as shown in the diagram, to enhance the joint forces and thereby accelerate wear. This study focuses  
Figure 2: Flowchart of the wear prediction process. solely on the wear at the joint between the connecting rod and the crank, referred to as the joint of interest in Figure 3.  
The simulated joint of interest comprises a 347 stainless steel journal and a polytetrafluoroethylene (PTFE)ushing, which facilitate the connection between the crank and connecting rod. The material properties of these components are listed in Table 2. The wear coefficient used in the simulation was derived from the study by [PERSON], [PERSON], et al. [28]. In that study, PTFE samples were machined to create a flat surface, while the 347 stainless steel counterface was wet-sanded to achieve an average roughness (\(R_{\mathrm{d}}\)) between 0.1 and 0.2 \(\upmu\)m. Wear tests were performed over a specified number of cycles under a predetermined load, resulting in a contact pressure of approximately 4.5 MPa. During the tests, the relative sliding speed averaged 73 mm/s. Further details about the testing procedure can be found in [28]. The simulated joint operates without lubrication and is subject to moderate loading and low-velocity sliding contact conditions. The selection of the journal and bushing materials aims to simplify the analysis, assuming that the steel journal is rigid, undergoing minimal deformation and negligible wear, while the PTFE bushing is deformable and experiences more substantial wear. Consequently, Equation (5) is applicable, as it is designed for contact scenarios where only one of the components is deformable. This study examines the effects of bushing depth, internal and external bushing diameters, and bushing rim thickness. The variables representing the different geometric \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Length (m)** & **Mass (kg)** & **Moment of Inertia (kg-m\({}^{2}\))** \\ \hline Connecting rod & 0.1016 & 0.8175 & 5500.0 \\ Crank & 0.0381 & 0.4045 & 204.0 \\ Slider & - & 8.5000 & – \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Properties of the slider–crank mechanism used in this study [24]. Figure 3: Slider–crank mechanisms indicating the joint of interest between the crank and connecting rod. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Title 1** & **Steel Pin** & **PTFE Bushing** \\ \hline Poisson ratio & 0.29 & 0.38 \\ Density & 7.8 g/cm\({}^{3}\) & 2.25 g/cm\({}^{3}\) \\ Young’s Modulus & 206.8 GPa & 0.500 GPa \\ Friction coefficient (steel and PTFE) [45] & & 0.13 \\ Wear coefficient (steel and PTFE) [28] & & 5.05 \(\times\) 10\({}^{-4}\) mm\({}^{3}\)/Nm \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Properties of the journal (347 stainless steel) and bushing (PTFE).