modeling and fem analysis of knuckle joint

MODELING AND FEM ANALYSIS OF KNUCKLE JOINT

1

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


2

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


3

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.


4

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


5

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


6

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.


7

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


8

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)


9

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)


10

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


11

=

=

= 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.


12

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.


13

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

http://mechteacher.com/knuckle-joint/