Analytical and Finite Element Assessments of the Structural Integrity of a Lawn Mower Blade

Lawn mower blade is an essential part of the unit as a machine. It is, therefore, necessary for its design to be formidable in order to prevent failure in service. This work presents analytical and finite element (FE) relationship of the structural integrity of a lawn mower blade. For the analytical (theoretical) approach, the blade was assumed as a rotating disc, while for the FEA a 3-D solid model of the mower blade was generated, discretized and loaded statically, at the cutting edge using Solid Works. A uniformly distributed load of 400 N/m was applied in both cases. From the results obtained, the maximum theoretical hoop stress value was about 47.4 MPa, while the maximum Von-Mises stress for FEA was about 49.42 MPa. That maximum hoop stress value was about 96% of the maximum Von-Mises stress value, which suggests a strong correlation and agreement between them, as they both occurred at the inner radius of the blade. The maximum theoretical hoop strain value was about 2.00 x 10 -4 mm/mm, while that of the maximum radial and FEA values were about 3.4 x 10-5 mm/mm and about 1.06 x 10-4 mm/mm, respectively. The maximum analytical displacement value was about 0.254 x 10-1 mm compared with FEA displacement value of about 2.50 x 10-1 mm. With the results obtained from both analytical and FEA approaches, the percentage analytical values relative to the maximum allowable values of stress, strain and displacement were about 17.9%, 77.8% and 2.3%, respectively, while the corresponding percentage of the FEA values to the maximum allowable stress, stain and displacement values were about 18.6%, 41.2% and 23.4%, respectively. The absolute percentage difference in stress between analytical value and FEA value was about 0.7%, while that for the strain and displacement values were approximately 36.6% and 21.1%, respectively. The difference in their respective corresponding values do not significantly affect the outcome of the results and their corresponding effect on the stress, strain and displacement. Overall, it was observed that the maximum stress, strain and displacement values obtained from both theoretical analysis and FEA were less than their corresponding allowable stress, strain and displacement values. With this result, the blade will not fail in service going by the induced stresses and assumptions adduced.