Determination of Physical and Mechanical Properties of Autumn Leaves of Maple, Bitter Orange, Oak, Boxwood, Yellow Poplar, and Brown Poplar Trees

Aims: The results will be used to design and construct a collecting device, specially the main sucking part.
Study Design: In order to determine the physical properties of autumn leaves, twenty leaves from each tree of maple, bitter orange, oak, boxwood, yellow poplar, and brown poplar were collected with the same shape found on the ground (wrinkled or crumpled).
Place and Duration of Study: Department of Agricultural Machinery, Faculty of Bio-System Engineering, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran, July and august 2012.
Methodology: The maximum length, width, and thickness, as well as mass of each leaf were measured in varied moisture, static friction coefficient, true density, bulk density, and porosity. To determine the mechanical properties of friction coefficient and discharge and filling angles, the limit velocity and shear strength were also measured in the leaves.
Results: Measurement of the leaves shear strength of maple, oak, bitter orange, boxwood, yellow poplar, and brown poplar showed the highest shear strength in brown poplar (0.085 MPa) and the lowest in maple (0.033 MPa). According to the measured aerodynamic properties of autumn leaves (maple, boxwood, yellow poplar, brown poplar, bitter orange, and oak), the velocity limit has increased by increasing moisture. The velocity limit increases by increasing moisture. Also the friction coefficient increased by increasing moisture.
Conclusion: Among the studied leaves, maple had the maximum mean of weight, the maximum length, and the maximum mean of thickness, while boxwood had the maximum density and the highest moisture. The highest and the lowest porosity belonged to maple leaves (96.17) and bitter orange leaves (95.88), respectively. The shear strength of maple, oak, bitter orange, boxwood, yellow poplar, and brown poplar leaves were 0.033, 0.034, 0.041, 0.038, 0.085, and 0.084 Mpa, respectively. The repose angle of filling and the angle of discharge of the six leaves in sum were 50º and 51º, respectively.