The Effects of Moisture Content, Compression Speeds, and Axes on Mechanical Properties of Walnut Cultivars

In this study, the mechanical properties of walnut (Juglans regia L.) cultivars were investigated as a function of moisture content. The experiments were carried out at three moisture contents, compression speeds (0.5, 1, and 1.5 mm/s), and compression axes (X-, Y-, and Z-axes). The highest rupture force and rupture power in all moisture contents were obtained for walnut cultivars loaded along the Y-axis. Rupture force, rupture energy, and rupture power of walnuts decreased in magnitude with an increase of moisture content, while rupture force, specific deformation, rupture energy, and rupture power increased with an increase of compression speeds. The highest rupture force was obtained with load along the Y-axis as 410.4 N and 394.3 N and also the highest rupture force was recorded at 1.5 mm/s compression speed as 260.7 N and 377.1 N for Yalova-1 and Yalova-3 cultivars, respectively. A linear force decrease was observed from 320.5 N to 196.4 N and from 492.7 N to 247.1 N with increasing moisture content from 11.46% to 23.16% and from 11.25% to 19.47% for Yalova-1 and Yalova-3, respectively. The highest rupture force, specific deformation, rupture energy, and rupture power were obtained at 1.5 mm/s compression speed, while the lowest rupture force was obtained at 0.5 mm/s compression speed for walnut cultivars. The lower rupture force and rupture power were obtained with load along Z-axis for Yalova-1 and Yalova-3 walnut cultivars. The results revealed that the higher compression speed and Z-axis could be recommended for cracking of shelled walnuts.