Static analysis of thrust bearing with lubrication hole variation in an automobile’s connecting rod

ABSTRACT


Introduction
The engine's connecting rod is a crucial component. It transfers the gas pressure at the top of the piston to the crankshaft, to make it work. The reciprocating inertial force of the piston and the pressure of the piston pin must be supported by the connecting rod [1]- [4]. Thus, it is necessary to analyze the strength of the material. Static analysis using software applications is one of the non-destructive methods of testing materials [5]- [9].
Bearing research to detect defects by focusing on the vibrations generated has been conducted [10], [11]. The variables studied include radial load, axial load, bearing rotational speed, lubrication type, adjustment, and number of rollers [12]- [15]. Meanwhile, to obtain the value of the damage level of the bearing, variations in vibration amplitude are added.
Static analysis research results show that the area where critical stress occurs is located at the radius (fillet) of a part. Theoretically, a part with a small radius will produce greater stress. Where, the smaller the radius, the smaller the surface area. Thus, it will increase the stress that occurs [3], [16], [17].
Connecting rod failure generally occurs due to friction or impact on the connecting rod. Identification of effective and efficient countermeasures against rod metal must be carried out so as not to damage other components [18]. This analysis is needed to determine the ability to withstand excessive pressure on the thrust bearing which has an impact on the occurrence of high stresses so that it reaches the critical value of material strength [19].
Analysis of the rod is required to ensure the longevity of the connecting rod and minimize damage [20]- [22]. Thus, the connecting rod can optimally transmit power from the combustion process to the crankshaft. If during the analysis process, a very high loading occurs on the connecting rod and the thrust bearing is unable to reduce or withstand the explosive force of the combustion process, it is necessary to replace the material or redesign the component [23]- [25].
This study was a static analysis of thrust bearings of a 1298 cc automobile under the forces acting during the combustion process. The main load was piston pressure which was transmitted to the connecting rod and thrust bearing. The thrust bearing material was annealed stainless steel (SS 201). The analysis was carried out to obtain a thrust-bearing design with various lubrication holes with better resistance.

Method
The research stages included designing parts and assemblies, determining material property values, determining parameters for static analysis, computation, and data analysis. The design stage involved drawing the connecting rod and thrust bearing of a 1298 cc automobile, as shown in Fig. 1.   Table 1 shows the material properties of the thrust bearings. Table 2 shows the placement of the fixed geometry and the loading that was implemented on the connecting rod. ---,---, -4785 N The next step was to set the mesh size using a curvature-based mesh with a maximum element size of 1.5 mm and a minimum element size of 0.499995 mm, as shown in Table 2. Meanwhile, the meshed connecting rod design can be seen in Fig. 3.   The simulation comprised simulations of stress, displacement, strain, the factor of safety, and stress in critical areas [26]. The simulation result of the thrust bearing is shown in Fig. 4.

Results and Discussion
The research results in the form of stress, displacement, and strain on various thrust-bearing designs are shown in Table 3. Meanwhile, the research results in the form of safety factors for various thrust-bearing designs can be seen in Table 4.  Stresses of various thrust-bearing designs can be seen in Fig. 5. The largest stress value is the onehole thrust bearing with a value of 215.1 MPa. At the same time, the thrust bearing with the lowest stress is the non-hole thrust bearing with a stress value of 52.51 MPa. Non-hole, one-hole, and three-hole thrust bearings can reduce the force by 52.75%, 26.34%, and 27.81%, respectively. Thus, the greater the percentage reduction in force or stress that occurs due to low loading at yield strength, the safer the material [2], [7]. So non-hole thrust bearing is the safest among other variations. The displacement values obtained from the three thrust-bearing variations can be seen in Fig. 6. The three-hole thrust bearing has the greatest displacement value of 2.710E-02 mm.

Fig. 6. Thrust-bearing displacement
This proves that the smaller the surface area of the thrust bearing, the more the displacement value will increase [1]. By expanding the cross-sectional area of the connecting rod by 30%, the distortion of the connecting rod's big end bearing was reduced by 4.3%.
The strain values obtained from the three thrust-bearing variations can be seen in Fig. 7. The threehole thrust bearing has the greatest strain value, namely 1.276E-03; this made the three-hole thrust bearing experience a large strain. On the other hand, the lowest value is the non-hole thrust bearing with a value of 8.531E-04, which caused the force that could be absorbed by the three-hole thrust bearing smaller than the non-hole thrust bearing.
The results of the safety factor analysis range from 1.357 to 7.526. This is in the range of previous research, where the simulation that has been carried out on the connecting rod produced a safety factor from 1.006 to 15 [4] [18]. The safety factor obtained for each specified material can be seen in Fig. 8 8 shows that the greatest safety factor is achieved by the three-hole thrust bearing of 7.526, but with a minimum value of a safety factor of 1.385. This value is lower than the minimum value of the nonhole thrust-bearing safety factor of 1.896. So, the non-hole thrust bearing is relatively the safest among other variations of the thrust bearing.
The critical area in the thrust bearing analysis occurred on the side of the lubrication hole, as shown in Fig. 9. The maximum stress that occurs is 227.2 MPa. Compared to the yield strength of the material, the material experienced a stress of 77.81% or a safety factor of 1.285. The safety factor is still safe because the value is greater than 1 [7], [26], [27]. The highest effect of loading occurred in the three-hole thrust bearing, which is equal to 77.81%. However, this is still below the yield strength limit of the material. So, it can be concluded that the material is still safe in critical areas.

Conclusion
Based on the results of the study it can be concluded that thrust bearings with non-hole could be the safest thrust bearing compared to the one-hole and three-hole variations. Non-hole thrust bearing had a critical stress area value of 1.540E+08 where it could absorb a force of 52.75% of the yield strength, the lowest strain was 8.531e-4, and the highest minimum safety factor of 1.896.