This report presents the structural analysis of knuckle joint using finite element analysis. The analysis considered the fracture failure of the structure from a loading of 70 kN axial load. It was found that the structure has a factor of safety of 2 for this loading and failure mode. The structure is therefore satisfactory for the desire design condition. The model is done with solid work and imported into Ansys. The FEM analysis had done with different mesh type and compared the result obtained. Further study in this direction can made by using various diameter of the pin, choosing the different material and the capacity to withstand load.

1. MODELING AND FEM ANALYSIS OF KNUCKLE JOINT
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University of Bridgeport
Spring 2016
Project Report
Modeling and FEM Analysis of Knuckle Joint
Course – MMEG- 453
Submitted by
Kanchha Lama (0991904)
Parth Patel (0989754)
Submitted to
Dr. J. Hu

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Index
Item No. Description Page No.
Summary ………………………………….. 3
1 Introduction ……………………………… 4
2
3
4
Structure Design/Problem Definition
Failure Scenario and Finite Element Model
Analysis Results
5-6
6-7
7-9
5 Verification 10-12
6
7
Conclusions
References
12
13

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Summary
This report presents the structural analysis of knuckle joint using finite element analysis. The
analysis considered the fracture failure of the structure from a loading of 70 kN axial load. It was
found that the structure has a factor of safety of 2 for this loading and failure mode. The
structure is therefore satisfactory for the desire design condition. The model is done with solid
work and imported into Ansys. The FEM analysis had done with different mesh type and
compared the result obtained. Further study in this direction can made by using various diameter
of the pin, choosing the different material and the capacity to withstand load.

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1. Introduction
The objective of this project was to design a knuckle joint structure to withstand with the
tensile load. A knuckle joint is used to transform the tensile load between the two rods in axial
direction. However, if needed the joint may also apply to compressive load. The knuckle joint
consists of different parts as following:-
1. Single eye.
2. Double eye or fork.
3. Knuckle pin.
4. Collar
5. Tapper pin.
Fig.1. the parts of Knuckle joint

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2. Structure Design/Problem Definition
The design of the knuckle joint structure is shown in Figure 2. The knuckle joint is made
of mild steel. In the design, the diameter of knuckle joint rod is 36 mm and can withstand with
maximum pull load of 70 kN. The joint is bolted; the fork end is joined with eye end with the
help of knuckle pin like a bolt. The knuckle pin is secured between the two eyes by a tapper pin
and collar. The total weigh of structure is ……
Figure 2. Geometry of Design
The dimensions of various parts of the knuckle joint are fixed by empirical relations as given below.
Diameter of rod = d
The diameter of pin=
Outer diameter of eye, = 2d
Diameter of knuckle pin head and collar, = 1.5d
Thickness of single eye or rod end, t = 1.25d
Thickness of fork, = .75d

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Thickness of pin head, = .5d
Other dimensions of joint shown in figure 2.
3. Failure Scenario and Finite Element Model
A knuckle joint may be failed on the following four modes:
1. Failure of solid rod in tension
2. Failure of knuckle pin in shear.
3. Tensile failure of fork end
4. Failure of eye end in crushing.
A finite element analysis was performed to determine whether the ultimate stress is exceeded
with given load. The structure was subjected to a tensile load on both ends. The analysis assumes
that the knuckle pin will remain fixed with a small amount of expand in rigid mount. The
analysis ignores the possibility of geometric non-linearity.
After completing the geometry, the model is then import in the ANYSY. Meshing is done
in ANSYS. The tetrahedral elements have been used for 3D domain. The meshing of domains
has been shown in fig.3.

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Fig. 3 Mesh
We used the different type of mesh and found the following results;
Mesh Type No. of Elements No. of Nodes
Coarse 11044 20790
Fine 15842 29514
Proximity on Faces
and Curvature with
coarse mesh
194022 310254
The material for the design is aluminum alloy. The properties of aluminum alloys are following
Material Properties Value Unit
Density 2770 Kg/m^3
Young’s modulus 7.1e+10 Pa
Bulk modulus .33
Tensile yield strength 2.8e+08 Pa
Ultimate tensile strength 3.1e+08 Pa
Compressive ultimate strength 0 Pa
Shear strength 2.07e+08 Pa
As boundary conditions varying load has been specified at eye and fork shafts. Taper pin, Collar
and knuckle pin are fixed. An axial load of 70 kN has been applied at the end of the joint.
4. Analysis Results
From the finite element analysis, it was found that stress as shown in Figure 4.a and 4.b. The
maximum stress was found to be 130.09 Mpa when we used the fine mesh and for the coarse
mesh we found the maximum stress of 80.65 MPa . The ANSYS analysis indicated the maximum

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stress experiences at the interface between the pin, eye-end and the fork end. The structure therefore
has a safety factor of almost 2 for this loading and failure mode. The structure is therefore
satisfactory for carrying the axial load of 70kN. When a load of 70 kN is applied in the system, the
ANSYS analysis shows that the maximum stress experience in the structure is 130.09 Mpa(fine mesh)
and 80.65 Mpa (coarse mesh) . It is clear that aluminum alloy shows maximum yield strength of 280
Mpa. So, from this it is clear that structure can sustain without failure under the axial tensile load of 70
KN.
Figure 4.a. Stress (Fine Mesh)
Figure 4.b Stress (Coarse mesh)

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ANSYS software has a unique module which able to measure the amount of deformation i.e.
change in length of the joints Fig. 5a and Fig. 5b shows a typical diagram illustrate the
elongations in each part of the knuckle joint. It may be mentioned that maximum deformation
experienced at the two ends of the joints and minimum deformation occurred around the pin
area. The above results show that the displacement at the two ends of the joints is around
0.097795m for fine mesh and 0.097781 for the coarse mesh. The minimum displacement which
is found around the pin is 0 mm in both cases. The analysis shows that the deformations
experienced by the components are less and can be use safely for the application.
Fig. 5.a Deformation (Fine Mesh)

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Figure 5.b Deformation (Coarse mesh)
5. Verification
To check the failure modes:
P= 70 kN
Diameter of rod = d= 36 mm
The diameter of pin= = 36 mm
Outer diameter of eye, = 2d = 72 mm
Diameter of knuckle pin head and collar, = 1.5d = 54 mm
Thickness of single eye or rod end, t = 1.25d = 45 mm
Thickness of fork, = .75d = 27 mm
Thickness of pin head, = .5d = 18 mm
We know that the allowable stress for the rod material,
= = = 140 Mpa
We know that the allowable shear stress for the rod material

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= = = 103.5 Mpa
1. Failure of solid rod in tension
P= ×
Therefore, 70000= × ×
= 68.77 Mpa
2. Failure of knuckle pin in shear
P=2× ×
70000= 2× ×
Therefore, = 34.4 MPa
3. Tensile failure of fork end
P= ( - ) 2
70000 = (72-36) ×2×27×
= 36 MPa
4. Failure of eye end in tension.
P= ( - ) t
70000 = ( 72-36) ×45 x
Therefore, = 43.2 MPa
From above results we can see that the induced stresses are less than the allowable stress so the
joint is safe.

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Also, from the Ansys analysis, we get the structure is safe under the axial load of 70 kN and the
rod diameter of 36 mm. Ansys results shows the maximum stress of 130.09 MPA ( fine mesh)
and 80.65 Mpa (coarse mesh). This is under the allowable stress of 140 Mpa by analytical
calculation. Therefore the knuckle joint will sustain under 70 KN axial loads.
6. Conclusion
The fem analysis has done with knuckle joint. To analysis the stress, mesh was developed for
the knuckle joint. The analysis has done with the different mesh type. After plotting the stress
contour, it is clear that the aluminum alloy knuckle joint with rod diameter 36 mm is capable of
taking the pull load of 70kN. ANSYS analysis gave the maximum stress of 130.09 Mpa in fine
mesh, which is less than the allowable maximum Stress by Al Alloy.

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References
1. Knuckle Joint – Introduction, Parts and Applications. Retrieved from
http://mechteacher.com/knuckle-joint/#ixzz45WN6ehJw
2. S. Das, V. Bartaria, P. Pandey. (2014, January). Analysis of Knuckle Joint of 30C8 Steel
for Automobile Application. International Journal of Engineering Research &
Technology
3. J. K. Gupta, R. S. Khurmi. (2005). A textbook of Machine design. Cotter and knuckle
joint. New Delhi : S. Chand