Tillage is one of important operations to improve and maintain surface soil in farm land. The
optimal tillage condition is dependent remarkably on the soil types as sandy soil or cohesive
soil, and soil conditions such as hardness, moisture content, and so on. Various tillage
methods and tools have been developed up to present. However mechanical interaction
between soil and tillage tool, and soil deformation and soil cutting phenomena during tillage
operation are very complex system in general. Therefor their developments have been often
conducted by experience and sense using trial and error methods. Logical and reasonable
developing method is required .to reduce the developing time and costs.
On the other hand, Cundall (1971) has proposed the discrete element method (DEM) to
describe mechanical behavior of granular materials. In this method, the mechanical behavior
of discrete elements is calculated sequentially by solving motion of equation for each
particulate element. The DEM has been widely utilized in various fields such as engineering,
civil and geotechnical engineering, agricultural machinery and postharvest engineering fields,
cf. e.g. an analysis of avalanche of rocks and earth, analysis of tillage by a vibrating subsoiler
(Tanaka, 2006), granular flow analysis of silo (Masson and Martinez, 2000), and so on.
Shmulevich (2010) have reviewed carefully soil-tillage tools interaction phenomena by twoand
three-dimensional DEM analyses and further have demonstrated the realistic soil-tillage
DE simulation results. Moreover, Hirasawa et al. (2010) have predicted soil throwing
behavior under a rotary tillage condition by DEM.
In this study, a tillage simulation model for a moldboard plow was developed by using a
commercial three-dimensional DEM code called the particle flow code (PFC3D, Itasca).
Drawbar pull, soil resistance on the plow, and soil deformation and soil cutting phenomena
were simulated under several tillage and soil conditions. The validity was verified by
comparing with experimental data.
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