A Constant Velocity Joint (CVJ) is a mechanical device capable of transmitting torque and motion between two rotating shafts that are misaligned. Most front wheel drive vehicles have torque and motion transmitted to the driven wheels through a set of inboard CVJ's (transmission side) and a set of outboard CVJ's (wheel side). One of the most common types of inboard joints is the Tripode Joint, which is composed of a housing, a spider and three sets of roller assemblies that connect the spider to the housing and allow for stroking motion and rotation of the joint at an angle. Wear fatigue-life in a Tripode Joint is defined by how many rotation cycles a Joint can complete before experiencing spalling or flaking of the internal surfaces subject to contact forces. Similarities and differences between a Tripode Joint and roller bearings are discussed. Internal contacts are treated as non-Hertzian and the state of stress is determined based on the kinematics of the joint, the geometry of the interacting components and the way internal forces are distributed when a torque is applied.A rolling contact wear fatigue-life model for Tripode Joints, that relates the critical shear stress in the contacts to the number of cycles a joint can perform before spalling, is proposed and compared to actual test data. Residual stresses were considered to obtain the stress-life exponent of the Tripode equation.Optimization of the geometric form of the contact surfaces in the spider is performed, aimed to minimize the peak contact load and to minimize the load differences between adjacent needle rollers. Reduction of the peak contact load allows an increment in durability of the Tripode Joint. The optimized profile in the contact surfaces of the spider is compared against traditional geometric forms, such as perfect circular and elliptical. The proposed model has a direct application in the auto-industry.
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