Hatem Bentaher

Study the effect of tool geometry and operational conditions on mouldboard plough forces and energy requirement

Experimental validation of FEM results in part 1 using soil bin.The effect of the depth and the speed on tillage forces.The influence of the cutting angle (α) and the lifting angle (β) on tillage forces.The influence of the cutting angles (α and β) on the soil loosening and inversion.The influence of the depth and speed on the soil loosening and inversion. Forces acting on tillage tools directly affect vehicle fuel consumption of tillage operations. Both tool forces and soil disturbance are a function of tillage tool type, tool geometry, and operational conditions. A soil bin experiment in a sandy loam soil was conducted to validate the results obtained from the finite element method (FEM) simulation of the interaction between soil and a mouldboard plough, carried out in part 1 of this study. An octagonal load cell was used to measure the draught and vertical forces. A special support was manufactured to modify the cutting angle (alpha) and the lifting angle (beta). Tillage forces and soil disturbance were measured for different speed (0.5, 1, 1.5, and 2m/s), depth (100, 150, 200, and 250mm), cutting (30?, 45?, 60?, and 75?), and lifting (25?, 40?, and 55?) angles, and were presented for the same soil conditions of those considered in the FEM. The soil disturbance including the width and surface area of the cut soil, and the height, width, and the surface area of the soil inversion were measured with a laser scanner. Results showed that both the FEM calculations and the soil bin measurement presented the same tendency for the variation of draught and vertical forces with speed, depth, cutting, and lifting angles. The maximum error recorded between the measured and the FEM results was 33.8%. It was found that the draught and vertical forces increased linearly with speed, whereas a second order polynomial and linear relationships were established with depth, respectively. Draught increased linearly with both the cutting and lifting angles, whereas, the vertical force decreased linearly with these angles. The study of the soil disturbance showed that the operating conditions (speed, depth, and cutting angles) of the mouldboard plough had an important effect on the quality of the tillage (soil loosening and inversion). Both the FEM and the soil bin tests showed that at a working speed of 1m/s and a depth of 150mm with lower lifting and cutting angles of 25? and 45?, respectively, provide the best combination for lowering energy consumption. The soil bin tests showed that these settings provide a good soil disturbance.

Finite elements modeling of olive tree mechanical harvesting using different shakers

The aim of this study is the optimization of stem shaking conditions in the mechanical harvesting of olive fruits. In order to study the influence of different shakers on the dynamic response of “Chemlali”, the main olive variety in Tunisia, a finite element numerical modeling was undertaken. The olive tree is modeled by three-dimension beams. Each beam has two nodes and 6 freedom degrees for each node. The structure is built by 560 elements and 561 nodes. For each part of the tree, the wood’s mechanical characteristics are determined experimentally. Orbital and multidirectional shakers were the mechanical harvesting tools tested. For each type, we developed the excitatory force equation as a function of the shaker’s characteristics: the eccentric value, the unbalanced weights and their rotation frequencies. In this paper, we present the structure response in relation to the shaker’s type, its placement and its excitation frequencies. This response was controlled, firstly by the acceleration and displacement values at the ends of secondary branches, and secondly by the reaction force at the peduncles level. These results are useful for the design of new shakers adapted to the studied olive variety.

A novel method to assess drought stress of olive tree

Threats of desertification have been projected for the Mediterranean basin under relatively minor warming and drying scenarios. This situation raises the need for mitigation strategies and adaptation of crop production. Crop vulnerability assessment is therefore needed. In Tunisia, olive culture is a major activity. In some cases, olive is the only crop able to grow in local conditions. However, olive production may be among the more vulnerable systems to climate change since perennial crops adapt slowly. No studies have been dedicated to vulnerability evaluation of olive production. Here, the vulnerability of Tunisian olive trees to drought was assessed under extremely low precipitation levels, of 50% of normal precipitation, from 1999 to 2002. The impact of drought was quantified using a severity scale with three levels. A map of the impact of drought on olive trees was constructed for all Tunisian olive groves. We found that the number of wilting olive trees in 2002 was 7.8 millions of about 60 millions trees. A correlation was observed between olive tree affection by drought and olive orchard age. Thus, under the same drought conditions, senescent orchards were less resistant to drought than young ones. Locally, data showed that compact soils and soils containing more than 1% gypsum were not suitable for olive growth under drought.