Practical Evaluation of Ball Stud Plating Effects on the Increase of Free Gap of Ball Joints in the Vehicle
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ght © 2020 KSAE/ 11704 pISSN 12299138/ eISSN 19763832
PRACTICAL EVALUATION OF BALL STUD PLATING EFFECTS ON THE INCREASE OF FREE GAP OF BALL JOINTS IN THE VEHICLE Soo Sik Chung1), Young Ze Lee2)* and Sang Oh Park3) Advanced Durability Development Team, Hyundai Kia R&D Center, 150 Hyundaiyeonguso-ro, Namyang-eup, Hwaseong-si, Gyeonggi 18280, Korea 2) School of Mechanical Engineering, Sungkyunkwan University, Gyeonggi 16419, Korea 3) R&D Center, Iljin Corporation, 527 Samseong-ro, Gangnam-gu, Seoul 06157, Korea
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(Received 24 October 2019; Revised 5 December 2019; Accepted 7 December 2019) ABSTRACTThe 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. KEY WORDS : Ball joint, Ball stud, Plating, Abrasion, Bearing, Lower control arm, Free gap, Abnormal noise, Clunking
1. INTRODUCTION A ball joint is a component that connects the vehicle suspension control arm and the steering knuckle. It transmits axial tension, compression force and radial force with the freedom of 3-axis rotation direction without torque transmission. With almost no elastic deformation, it is possible to implement directive handling performance (Crolla, 2009; Duffy, 2017). As shown Figure 1, in the structure of ball joint, there is a ball stud in the socket with a synthetic resin bearing in between. Grease is applied to the contact surface of the ball stud inside the bearing to smooth the rotational and oscillatory movements of the ball stud. Also, the set-up includes a dust cap to prevent foreign matter from entering. Figure 1 shows the position and detailed structure of the ball joint connecting the front lower control arm to the steering knuckle (Halderman, 2010; Han et al., 2017). However, in the case of some vehicles operated under 30 ℃ tempera
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