Heavy duty vehicle differential carrier optimization and design with QT500-7 material

Heavy duty vehicles could be defined as a vehicle which is used to carrying cargo, construction goods or other kind of servics. They have many different usage area and the most of OEMs (heavy duty vehicle manufacturers) are specilazied for only heavy duty market. Generally, heavy duty trucks are classified according to their carrying capacity (20tns, 40tns) or usage area (road truck, construction truck, trailer). As another classification, and more specialized, trucks are defined according to their powertrain characteristics. Rear axle and differential arrangement is one of these powertrain specifications. Trucks are defined as their axle arrangements (singe axle, twin axle) or differential system arrangements (single reduction, hub reduction etc.) Differential system is implemented to vehicle in order to provide issueles usage during cornering. Cornering causes different angular velocity and torque sharing on rigth and left wheels and have to be compansated by extra system which provides torque and rotating movement sharing from proppeler shaft to wheel hubs. The system consists of a pinion, ring gear, differential carrier and side gears and is a kind of planetary gear system. Pinion takes rotational speed and torque from propeller shaft and transmits to ring gear. Ring gear is mounted to differential carrier and it rotates carrier with torque and speed which is came from pinion according to differential ratio. Side gears are mounted on a bar or cross (according to side gear number). Heavy duty trucks usually have four side gears and it means cross mounsted side gears. Cross provides mounting to side gears and rotates with differential carrirer. Side gears are meshed with shaft gears. Shaft gears are mounted on axle shafts and they rotate and transmit torque to wheels. Carrier is mounted to axle housing with two bearings and works under ring gear loading. Pinion and ring gear are designed using with a CAE tool which is specialized for hypoid and bevel gear design. Macrogeometry and microgeometry parameters are calculated with this tool. This tool also provides diametral data and loading data of ring gear. Diametral data is used for CAD study to create a 3d model. It is accepted as a design constraint by designer. This model has high volume and used to conduct topology optimization analysis. Topology optimizatin analysis is type of optimizain analysis which gives an idea abour material requirements and arrangemens on final design. Topology optimization models are created using with a pre-processor CAE tool. Ring gear is added to model in order to apply gear loading. Boundary conditions are specified to provide more representative CAE model. Bearing interfaces and and cross spline have different constraints. Topology optimization analysis is conducted under these conditions and results are post-processed carefully. Volume and strain energy density are used as objectuve function and design constraint. In addition to that, manufacturing constraints are implemented to optimization analysis. These are rotational symmetry and molding direction. As nature of topology optimizatin analysis, results are not clear or well-understood. They must be evaluated by an experienced designer. Output files of optimization cannot be used directly. A new CAD model must be created according to optimization analysis results. New model have to be appropriate for manufacturing constraints and met durabilty targets. Durability analyses are done to predict critical sections and potential design improvements. Durability analysis step is an iterative process because a design change migth be cause a failure from another section of carrier. For this reason, carrier design is evaluated carrefully. Prototype of inal design of carrier must be tested according to standard design release methods. These method generally defined by independent standard organizations or experienced OEMs. After the test approvals, optimized differential carriers are ready to implement to vehicles.