Practical Evaluation of Ball Stud Plating Effects on the Increase of Free Gap of Ball Joints in the Vehicle

Abstract

The abnormal noises, such as clunking and popping, are usually generated when the car turns or drives over bumps. It could happen frequently when the free gap (clearance) values in the axial direction of the lower control arm ball joint are higher than normal values. The spherical surface of the ball stud is commonly assumed to have been corroded by foreign substances such as water, and the rough surface of the corroded ball stud accelerates the abrasion of the bearing contact portion to increase the free gap. Thus, the dust cap material and shape have been improved over time. However, there are still recurrences. The objective of this study was to evaluate two ball studs with different plating thicknesses and one uncoated sample from the reproducibility test simulating vehicle behavior conditions under environment test conditions. The findings of this study were as follows: First, the ball stud plating is advantageous in corrosion resistance, however, the thickness of the plating is uneven and the surface becomes rough with time, thereby accelerating the abrasion of the bearing contact portion. Second, as the surface of the ball stud wears, oscillating torque decreases and the axial free gap increases, which is more disadvantageous as the thickness of the ball stud sphere becomes thicker. Therefore, uncoated ball joint was defined as the best option.