R. Hemmatian - Department of Mechanics of Agricultural Machinery, Faculty of Agriculture, Tarbiat Modares University, Tehran, P. O. Box: ۱۴۱۱۵-۳۳۵, Islamic Republic of Iran.
G. Najafi - Department of Mechanics of Agricultural Machinery, Faculty of Agriculture, Tarbiat Modares University, Tehran, P. O. Box: ۱۴۱۱۵-۳۳۵, Islamic Republic of Iran.
B. Hosseinzadeh - Department of Mechanics of Agricultural Machinery, Faculty of Agriculture, Tarbiat Modares University, Tehran, P. O. Box: ۱۴۱۱۵-۳۳۵, Islamic Republic of Iran.
T. Tavakkoli Hashjin - Department of Mechanics of Agricultural Machinery, Faculty of Agriculture, Tarbiat Modares University, Tehran, P. O. Box: ۱۴۱۱۵-۳۳۵, Islamic Republic of Iran.
M. H. Khoshtaghaza - Department of Mechanics of Agricultural Machinery, Faculty of Agriculture, Tarbiat Modares University, Tehran, P. O. Box: ۱۴۱۱۵-۳۳۵, Islamic Republic of Iran.

In the present study, shearing properties of sugar cane stems were determined at five moisture content levels (۴۶, ۵۴, ۶۲, ۷۰ and ۷۸% wb), three shearing speed (۵, ۱۰ and ۱۵ mm min-۱) and at ten positions on the stem. For measuring the shearing forces, the stems were severed by using a computer aided cutting apparatus. Decrease in moisture content of stem from ۷۸ to ۴۶% wb led to ۱۶.۳ and ۱۶.۷% decrease in the shearing strength and specific shearing energy, respectively. The maximum and average values of shearing strength of the two moisture contents were found to be ۳.۴۸۲ and ۳.۱ MPa, and the specific shearing energies were ۱۱۲ MJ mm-۲ and, ۱۰۲.۶ MJ mm-۲, respectively. Both the shearing strength and the specific shearing energy were found to be higher in the lower region of the stem due to structural heterogeneity. Results showed that with the increase in shearing speed from ۵ to ۱۵ mm min-۱, shearing strength and the specific shearing energy increased ۳.۲ and ۴.۶%, respectively. The results of ANOVA indicated that effects of the mentioned factors were significant at ۱% probability level. The shearing model assessment revealed that the third order polynomial model exhibited the best performance in fitting with experimental data and, by using this model, a significant correlation was found between shearing strength, specific shearing energy, and moisture content (R۲= ۰.۹۸۹ and SE= ۰.۰۰۱). Also, a significant correlation was found between shearing strength, specific shearing energy, and shearing speed by using Hoerl model (R۲= ۰.۹۸۹ and SE= ۰.۰۰۵).

Mechanical properties of stem, Shear Strength, Specific shearing energy, Sugar cane