Stress analysis of additive manufactured lightweight spur gears

Abstract

Additive manufacturing processes (AMP) have grown and spread in the last twenty years. Additive manufacturing methods, which were first used for plastic materials, are now increasingly finding a place in metals. With these methods, more lightweight component designs which cannot be generated with traditional methods can be manufactured. With the spreading of electric drive vehicles, weight reduction is becoming more important since weight is primarily responsible for energy consumption. There is a one-stage gear system in electric vehicles in general. For this reason, the subject of reducing the mass of gears is gaining importance. The weight reduction can be achieved with holes and slots on the gear body for involute spur gears or reducing gear web thickness. Several optimization methods can be used for this aim. Another way is to use light materials for the gear body, while steel material is used in the tooth-rim region. Carbon fiber composites are preferred for this purpose. However, using adhesives to join steel and carbon fiber reinforced plastics may cause problems in different environmental conditions. On the other side, parts are generated with single material with AMP methods. In this study, involute spur gears with different designs convenient for generation by AMP are created in a 3D CAD program. The involute tooth region is defined as design space. The effects of different designs on root stress and tooth stiffness are investigated by finite element analyses. For this purpose, the mathematical modeling of involute spur gear is set to get points of a tooth based on Litvin's approach in MATLAB. A point cloud code is obtained and imported to the 3D CAD program. After that, three teeth 3D finite element spur gear models are generated. Static analyses are conducted in ANSYS. Meshing force is implemented on the highest point single tooth contact line. Root stress value is the most important reason for tooth root fatigue, one of the most common failure modes of involute spur gears. Tooth deflection and stiffness are significant parameters for the dynamic behavior of involute spur gears. The tooth stiffness affects mesh stiffness and transmission error which are the primary source of gear whine. For these reasons, tooth root stress and tooth deflection values should be determined for different gear designs.In this study, stress analyses of additive manufactured gears are conducted with the finite element method. The effect of shell thickness, infill radius, and infill stiffener on tooth root stress and deformation is recorded. According to the results, shell thickness is the most effective parameter on the root stress and deformation. It is followed by infill orientation angle and infill radius, respectively.