Improved Lawnmower Blade Design and Optimization Available to Purchase

With an estimated three billion man-hours of use each year, improvements to the mechanical efficiency of lawnmower systems may yield significant reductions in emissions. Modifications to either the blade geometry or material have been considered in order to achieve the desired gains in efficiency. Specifically, focus is placed upon identification of a more efficient edge shape, reduction of required power input to the blade, and extending the life of the blade sharpness. Using software packages such as Parametric Technology Corporation’s (PTC’s) Pro/Engineer the students were able to increase the quality of design via finite element analysis (FEA) programs such as MSC. Nastran or PTC’s Mechanica. AISI 440C stainless steel was selected as a possible candidate based upon several appealing properties such as high strength, hardness, and resistance to corrosion. It does however have a lower fracture toughness and therefore presents a higher susceptibility to brittle fracture. When both the traditional stress analysis and fracture analysis were considered, opposing results were found. Due to this, other criteria such as cost of material, machining costs, and carbon footprint were considered before making a final design decision. Enhancing education in engineering by diversifying design criteria and encouraging students to address contemporary, real-world design problems was a primary goal of this project. The traditional mechanical design approach relies on stress-strain analysis in order to predict potential failure scenarios, and is the primary technique presented in most undergraduate engineering curricula. Despite its significance, the fracture mechanics approach is not often presented in great detail at the undergraduate level. The academic benefits of including these more universal considerations in the undergraduate engineering curriculum are illustrated in this paper.