Analyze the Failure of a Suspension System Ball Joint
Swati K. Dhamale, Nirmala H. Bhingare
Assistant Professor, Department of Mechanical Engineering, D. Y. Patil College of Engineering, Akurdi, 411044
*Corresponding Author Email: paithankars22@gmail.com, nirmalab115@gmail.com
ABSTRACT:
This research gives the detailed understanding about the analysis and the causes of abrupt failure of a suspension system ball joint. The necking region which is between the top and bottom portion of ball joint showed total. It shows that ball joint fails completely and this is dangerous case. To avoid the sudden failure of ball joint design modification is required at the necking region. In this study, modification of ball joint design is done for this purpose. Design of ball joint is optimized also stresses raisers are removed for required outcome. It is examined that the modified ball joint gives the better results and life cycle of component is increased. The shear stress calculated by FEA results of ball joint is correlated with UTM test results.
KEYWORDS: Ball joint, Design modification, Life cycle, Necking, UTM.
INTRODUCTION:
Ball joint is used in the front end of every vehicle. It is the main part of entire system. It operates as pivot among the suspension system and ball joint. The weight of vehicle is supported with the help of ball joint. It consists of stud and socket. These parts are made of steel enclosed in steel casing. Socket is coupled to the control arm. Ball joint is tapered at the bottom to fit in the steering knuckle. And finally it is connected to the tire of the vehicle. It is the most critical part of any system. The ball joint is capable to move in all the directions. If they are used for long time, it may wear. Grease is used to reduce the wear between the two parts. The ball joint may fail if there is leakage of grease inside the system. The front suspension system ball joint fails due to many reasons so it is necessary to study the exact reason of failure of ball joint.
Suspension is the system of tires, tire air, springs, shock absorbers and linkages that connects a vehicle to its wheel and there is comparative motion among the two. Suspension system holds both road and ride quality. It is significant, that the suspension system needs to maintain wheel in contact with the road surface. It protects the vehicle from damage and wear of parts.
Experimentally the UTM is performed to determine the shear strength of ball joint [1]. Using the FEA software the analysis of ball joint is done. As the stresses in ball joint are more it is necessary to make the design modification to reduce the stress and improve the life of ball joint.
Material selection is also characterized by SN curve. SN curve shows that as the stress of ball joint is reduced the life is increased.
The ball joint is design using CATIA software. The model is then imported to ANSYS software. Dimension of suspension system ball joint is mentioned in table I below and design of ball joint as shown in figure 1.
TABLE I DIMENSION OF SUSPENSION SYSTEM BALL JOINT
Diameter 
Dimensions 
D1 
30 
D2 
20 
D3 
15 
Fig. 1. 3D CAD model of ball joint
Material properties assign to the model is listed below:
EN 18D Steel Alloy:
· Yield stress= 565 MPa
· Ultimate tensile strength= 887 MPa
· Density = 7.85g/cm3
· Poisson’s ratio = 0.29
Different mesh techniques are used to discretize the model. A tetrahedral method is used for meshing of ball joint, figure 2. The total number of elements 18740 and number of nodes 31686 are generated.
Fig. 2. Meshing of ball joint
A load of (2*575*9.81) N is applied to stud in downward direction and a load of (2*575*9.81) N is applied horizontally at a point of contact. Fixed boundary condition is applied to the socket. A force of 11400N is applied in Z direction. Figure 3 shows the boundary conditions.
Fig. 3. Boundary Conditions
By applying the calculated load to the ball joint following results are obtained as shown in figure 45.
Fig. 4. Equivalent VonMises Stress
Fig. 5. Fatigue Life
It is observed, as the equivalent vonmises stress exceeds the ultimate tensile strength of the given material, the ball joint fails due to crack initiation after applying the boundary conditions and crack leads to fatigue failure of ball joint.
After knowing the results, diameter of ball joint D3 is changed from 15mm to 16, 17 and 18mm to reduce the stress generated and increase the life of ball joint.
Fig. 6. Equivalent VonMises Stress
Fig. 7. Fatigue Life
Above figure 67 shows that the equivalent vonmises stress is 561.5MPa which is less than the ultimate tensile strength i.e. 887MPa and the yield stress i.e. 595MPa.
TABLE II COMPARISON OF RESULTS
Sr. No 
Diameter (mm) 
Equivalent Stress (MPa) 
Life (cycles) 
1 
15 
922.4 
293.5 
2 
16 
814.51 
405.6 
3 
17 
700.2 
601.02 
4 
18 
561.5 
964.58 




Table II shows the comparison of results for stress and fatigue analysis of modified ball joint i.e. 16, 17 and 18mm diameter. Hence design of ball joint is modified and stresses have been improved compared to previous design of ball joint.
Fig. 8. SN curve
The figure 8 shows the SN curve which indicates that as the stress value decreases the life of ball joint has been increased.
Objective of the tensile test is to determine the stressstrain behavior of a material and to analyze the result of tensile test. During shear test first the ball joint was held on the lower table and the force was applied in downward direction. After performing the shear test shear strength of ball was obtained. The shear strength of ball joint obtained is 529.31 MPa [1].
Fig. 9. Maximum Shear Strength
Above figure 9 shows the maximum shear strength of ball joint is 513.13MPa.
TABLE III COMPARISON OF RESULTS
Reference result 
529.31 
Modeling result 
513.13 
By experimental analysis shear strength of ball joint was found to be 529.31 MPa whereas on Structural analysis of ball joint the maximum shear strength is 513.13 MPa as shown in table III. The variation in experimental and analysis result is approximately 3% which is acceptable.
The results for stress and fatigue analysis of ball joint with boundary condition for previous model shows that the stress limit has crossed and the stress value is much higher than the ultimate tensile strength of the material. To improve the stress values the design of ball joint is modified. The newly design ball joint is safe and reliable. Design of ball joint is optimized also the stress raisers are removed. The newly design ball joint is safe. The modified ball joint shows that the obtain result of stress is improved and within the safety limit.
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Received on 05.03.2019 Accepted on 25.04.2019 ©A&V Publications all right reserved Research J. Engineering and Tech. 2019;10(2):9498. DOI: 10.5958/2321581X.2019.00016.3 
