18-12-2012, 05:28 PM
DESIGN OF CONNECTING ROD OF INTERNAL COMBUSTION ENGINE:
A TOPOLOGY OPTIMIZATION APPROACH
1DESIGN OF CONNECTING.pdf (Size: 258.25 KB / Downloads: 124)
ABSTRACT
This paper presents the design connecting rod of internal combustion engine using the
topology optimization. The objectives of this paper are to develop structural modeling,
finite element analyze and the optimization of the connecting rod for robust design. The
structure of connecting rod was modeled utilized SOLIDWORKS software. Finite
element modeling and analysis were performed using MSC/PATRAN and
MSC/NASTRAN software. Linear static analysis was carried out to obtain the
stress/strain state results. The mesh convergence analysis was performed to select the
best mesh for the analysis. The topology optimization technique is used to achieve the
objectives of optimization which is to reduce the weight of the connecting rod. From the
FEA analysis results, TET10 predicted higher maximum stress than TET4 and
maximum principal stress captured the maximum stress. The crank end is suggested to
be redesign based on the topology optimization results. The optimized connecting rod is
11.7% lighter and predicted low maximum stress compare to initial design. For future
research, the optimization should cover on material optimization to increase the strength
of the connecting rod.
INTRODUCTION
Connecting rods are highly dynamically loaded components used for power
transmission in combustion engines. The optimization of connecting rod had already
started as early year 1983 by Webster and his team. However, each day consumers are
looking for the best from the best. That’s why the optimization is really important
especially in automotive industry. Optimization of the component is to make the less
time to produce the product that is stronger, lighter and less cost. The design and weight
of the connecting rod influence on car performance. Hence, it is effect on the car
manufacture credibility. Change in the structural design and also material will be
significant increments in weight and performance of the engine. Mirehei et al. (2008)
were performed the study regarding the fatigue of connecting rod on universal tractor
(U650) by using ANSYS software application and the lifespan was estimated.
OPTIMIZATION APPROACH
The objective of optimization technique is to minimize the mass of the connecting rod
and reduce the cost of production. The connecting rod subjected to tensile load at crank
end, while using factor of safety 3 as recommended by Shenoy (2004). The maximum
stress of the connecting rod monitored and make sure it is not over the allowable stress.
The load of the connecting rod optimized is comprised of the tensile load of 26.7 kN at
crank end. Linear buckling analysis was performed on the connecting is 26.7 kN. The
buckling load factor is considered also 3. The optimization technique methodology
flowchart is shown in Figure 1.
RESULTS AND DISCUSSION
This section presents the details results of FE Analysis, selection of the mesh type and
influence of mesh type, identification of mesh convergence and optimization of the
connecting rod.
Influence of Mesh Type
The tetrahedral meshing approach is employed for the meshing of the solid region
geometry. Tetrahedral meshing produces high quality meshing for boundary
representation of solid structural model. Since the tetrahedral is found to be the best
meshing technique, TET4 was used for the initial analysis. The comparison then are
made between the TET4 and the 10 nodes tetrahedral (TET10) element mesh while
using the same global mesh length for the highest loading conditions (26.7 kN).
Material properties play an important role in the result of the FE analysis. The material
properties are one of the major inputs to perform the FEA and optimization. C-70 steel
is The mechanical properties of C-70 steel are shown in Table 1. From the results, it can
be found that the TET10 mesh predicted higher von Mises stresses than that TET4
meshes are known to be dreadfully stiff (Rahman et al., 2007, 2008b). TET4 employed
a linear order interpolation function while TET10 used quadratic order interpolation
function (Wang et al., 2004). For the same mesh size, TET10 is expected to be able to
capture the high stress concentration associated with the bolt holes. A TET10 was then
finally used for the solid mesh. Mesh study is performed on FE model to ensure
sufficiently fine sizes are employed for accuracy of calculated results but at
computational time (CPU time). Figure 4 shows the von-Mises stresses contour for
TET10 meshes element at a high load level.
Identification of Mesh Convergence
The convergence of the stress was considered as the main criteria to select the mesh
type. The finite element mesh was generated using the TET10 for various mesh global
length. It can be seen from Figure 7 that mesh size of 4 mm is obtained largest stresses.
The smaller size less than 4 mm do not implemented due to the limitation of CPU time
and storage capacity of the computer. Hence, the maximum principal stress based on
TET10 at 4 mm mesh size is used in the analysis since the stress is higher compared to
von-Mises, Tresca and maximum principal stresses.
CONCLUSION
The modeling of connecting rod and FE Analysis has been presented. Topology
optimization were analyzed to the connecting rod and according to the results, it can be
concluded that the weight of optimized design is 11.7% lighter and maximum stress
also predicted lower than the initial design of connecting rod. The results clearly
indicate that the new design much lighter and has more strength than initial design of
connecting rod. Material optimization approach will be considered for future research.