The deformation curve characteristics of rapeseeds and sunflower seeds compressed using the equipment ZDM 50-2313/56/18 and varying vessel diameters (40, 60, 80, and 100 mm) were investigated. Maximum compressive force of 100 kN was applied on bulk oilseeds of rape and sunflower of measured height 20-80 mm and deformed at a speed of 60 mm∙min-1. The compression test using the vessel diameters of 40 and 60 mm showed a serration effect while the vessel diameters of 80 and 100 mm indicated an increasing function effect on the force-deformation characteristic curves. Clearly, the increasing function effect described the region with oil flow and that of serration effect described the region without any oil flow. However, it was observed that the serration effect could be due to the higher compressive stress inside the smaller vessel diameters (40 and 60 mm) compared to those with bigger vessel diameters (80 and 100 mm). Parameters such as deformation, deformation energy, and energy density were determined from the force-deformation curves dependency showing both increasing function and serration effect. The findings of the study provide useful information for the determination of specific compressive force and energy requirements for extracting maximum oil from oilseed crops such as rape and sunflower.

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The present research is a follow-up of the previous studies on mechanical behaviour of Jatropha curcas L. seeds under compression loading. The research describes in detail the deformation energy which was determined from the area under the force-deformation curve. The compression device ZDM 50-2313/56/18 with a chart recorder and pressing vessel of diameter 76 mm were used to record the force-deformation functions of varying moisture content between 8.46% and 36.50% w.b. of Jatropha curcas L. seeds. Under the force-deformation curve, three main descriptions namely the increasing function (smooth curve), wave-effect characteristics (serration effect) and whole area under the force-deformation curve were analysed. For each of the force-deformation curve descriptions, it was found that moisture content influenced the values of compressive force, deformation, deformation energy and seed hardness. Interestingly, the research findings conclude that moisture content is a primary factor contributing to the wave-effect characteristics on the force-deformation curve.  

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A b s t r a c t. This paper evaluate the use of a tangent curve mathematical model for representation of the mechanical behaviour of sunflower bulk seeds. Compression machine (Tempos Model 50, Czech Republic) and pressing vessel diameter 60 mm were used for the loading experiment. Varying forces between 50 and 130 kN and speeds ranging from 10, 50, and 100 mm min -1 were applied respectively on the bulk seeds with moisture content 12.37±0.38% w.b. The relationship between force and deformation curves of bulk seeds of pressing height 80 mm was described. The oil point strain was also determined from the different deformation values namely 30, 35, 40, and 45 mm at speed 10 mm min -1 . Based on the results obtained, model coefficients were determined for fitting the experimental load and deformation curves. The validity of these coefficients were dependent on the bulk seeds of pressing height, vessel diameter, maximum force 110 kN, and speed 10 mm min -1 , where optimal oil yield was observed. The oil point was detected at 45 mm deformation giving the strain value of 0.56 with the corresponding force 16.65±3.51 kN and energy 1.06±0.18 MJ m -3