The Analysis of the Connection of Two Tools of a Modular Device for Soil Application of the Digestate

The issue of connecting two collaborating tools in the scope of determination of forces occurring in the hitch of the tools was discussed. The analysis was carried out at the example of a modular device for soil application of digestate. In one working pass the device enables to organize a work enabling evenly spreading the digestate at the soil surface, mixing it and covering with soil. Finite Element Method (FEM) numerical methods have been used for the development of a construction which allowed, among others, the determination of loads at the point of the tools connection. Carrying out experimental research in real conditions of operation, stress distribution and force values occurring in connection were determined. The force values obtained were verified with computer analysis carried out at the 3D model of the device, demonstrating the correctness of the assumptions made. INTRODUCTION Care for soil environment and in particular the content of humus in soil is one of the assumptions of sustainable agriculture. The increase of humus in the soil may be obtained, among others, by means of the use of natural fertilizers, including, among others, digestate. In order to enable this process while meet the requirements for the use of natural fertilizers, a modular device for subsurface injection of digestate was elaborated. The principles of ecodesigning, ergonomics and work organization in sustainable agriculture were implemented when elaborating the construction of the modular device (Bohdal et al., 2014; Kukiełka et al., 2016). The set consists of a manure spreader and a trailed disc harrow. The device offers the possibility of work organization enabling the simultaneous transport, spreading and mixing of digestate with soil. A bracket with a transport hitch developed according to the principles of ergonomics, mounted to the spreader frame, was used to connect both machines. This type of attachment ensures the transfer of loads generated by the aggregated disc harrow. The disc harrow is equipped with a drawbar ended with an eye. High strength requirements are set for connections of such kind, subject to variable and different operational loads. In order to define the level of loads at the point of connection, Finite Element Method (FEM) numerical methods were applied (Savaidis and Vormwald 2000; Maggi et al., 2005; Rakowski and Kacprzyk 2005; Wang 2012; Kosterski et al., 2016). They are commonly applied in the Industrial Institute of Agricultural Engineering, in the scope of elaboration of the construction of agricultural machines working with variable operating loads (Szczepaniak and Pawłowski 2005; Zbytek et al., 2013; Kukiełka et al., 2016). Moreover, computer simulations which enable to verify the adopted constructional solutions of agricultural machines are performed (Szczepaniak and Pawłowski 2005; Zbytek et al., 2009; Pawłowski et al., 2012; Wojciechowski 2013). Verification of obtained parameters takes place in real conditions, during the operation of the machine. Various kinds of test runs are considered in the regard. The results obtained are verified with results obtained in the simulation test.