Optimization of connecting rod of MF-285 tractor

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Introduction
In order to reach sustainable agriculture and to increase mechanization
level quality and manufacturing technology of agricultural machinery and also
its quantity must be reached to optimum level. One of the most important
agricultural machinery is tractor that has main share in planting, retaining and
harvesting operations and then in mechanization sector. Tractor MF-285 is
main production of Iran Manufacturing Tractor Co. Previously researches
showed that engine inner parts’ faults of MF-285 are more than other
ingredients of this tractor (Mahmoodi and Rezakhah, 2007).


Calculating forces exerted on crank end:
The combustion pressure force doesn’t have effect on crank end, but it is
affected by inertia force (Jangi, 2004). Also, screws in crank end are over load.
Always, they preloaded 2 to 3 time related to the maximum inertia force to
prevent departing of two bearing cup (Froozanpoor, 1997). Inertia force results
tensile stress and preloading force results pressure stress in crank end of
connecting rod. Preloading (MPa) in screws to page link bearing cup and above part
of crank end strongly and also to prevent screws’ breaking is equal to:


Modeling, meshing and loading forces on connecting rod
After calculating forces exerted on different parts of connecting rod in
most critically state, it was modeled and meshed in ANSYS (Ver.9) software.
Solid92 element was considered to carry analyzing. This element is three
dimensional with 10 nods. Also, this element related to Solid72 is better
specially, in problems with curve bounds had more accuracy, but it increases
time need to solve problems. Material qualification was considered as shown in
Table 2. To calculating stress in each connecting rod parts, calculated forces for
each parts was exerted on corresponding parts in modeled connecting rod in
ANSYS software’s medium considering following notes: