Title: Mechanical shear and tensile characteristics of selected biomass stems Authors
Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 31, 2012
Publication Date: August 27, 2012
Citation: Yu, M., Cannayen, I., Gustafson, C., Hendrickson, J.R., Sanderson, M.A. 2012. Mechanical shear and tensile characteristics of selected biomass stems. Meeting Proceedings. Paper #121337358. Interpretive Summary: Mechanical strength properties of biomass, such as tensile and shear stress and energy, are important quality attributes that influence operations such as chopping and grinding. These properties are determined using a Universal Testing Machine (UTM), where with special fixtures, the biomass was applied enough force made a failure, and the UTM continuously records the applied force. Biomass stems, such as big bluestem, bromegrass, and Barlow wheat were tested. Bromegrass was found to be a tougher, hence required more grinding energy, than other biomass studied. As the shear-based failure force is <34% of the tensile-based failure for the biomass species tested, the shear-based grinding equipment (e.g. knife mill or chipper) will be more efficient than other grinding devices.
Technical Abstract: Mechanical characteristics (stress and energy of tensile and shear modes) of selected biomass stems, such as big bluestem, bromegrass, and Barlow wheat were determined. A high capacity MTI-100K universal testing machine attached with standard tensile clamps and designed fabricated double-shear device were used for shear and tensile testing, respectively. Ultimate tensile stress and specific tensile energy values were statistically similar, while the shear stress and specific shear energy values were significantly different for the selected biomass stems. Ultimate shear stress and specific shear energy of bromegrass stems were significantly different (p<0.0001) from big bluestem and wheat stems, recording a largest value of 10.5 MPa and 27.0 kN/m, respectively. Stress values of shear failure mode were significantly smaller than tensile failure mode with evaluated shear to tensile stress ratios were 26.8%, 33.7%, 27.3%, while shear to tensile energy ratios were relatively constant as 54.3%, 55.1%, 54.0% for big bluestem, bromegrass, and wheat stems, respectively. Based on results, shear-dominant size reduction devices (e.g. knife mill, chipper) tend to be more energy efficient and this feature should be taken advantage of while designing size reduction devices. output.