DEPARTMENT OF APPLIED MECHANICS

A REPORT ON

FINITE ELEMENT ANALYSIS OF KNUCKLE JOINT

SUBMITTED TO SUBMITTED BY

Dr. D. K. SEHGAL JEETENDRA DAMADE

(2011AMD3447)

INDEXSR. NO. CONTENTS PAGE NO.

1 Abstract …………………………………………………….

2 Introduction…………………………………………………

3 Applications ……………………………………………….

4 Mode of failure……………………………………………..

5 Methodology of stress analysis…………………………….

6 Results………………………………………………………

7 Conclusions…………………………………………………

Abstract:

knuckle joints are most common in steering and drive train applications where you need to move something (steering linkage etc.) but also need to allow for offset angles. A knuckle joint is used to connect the two rods which are under the tensile load, when there is requirement of small amount of flexibility or angular moment is necessary. There is always axial or linear line of action of load. For analysing the stress and displacement first making the catia model of the knuckle joint and then FEM analysis is carried out.

Introduction

A knuckle joint is used to connect two rods which are under the action of tensile loads. However, if the joint is guided, the rods may support a compressive load. A knuckle joint may be readily disconnected for adjustments or repairs. Its use may be found in the link of a cycle chain, tie rod joint for roof truss, valve rod joint with eccentric rod, pump rod joint, tension link in bridge structure and lever and rod connections of various types.

Fig.1 knuckle joint

In knuckle joint (the two views of which are shown in Fig. 1), one end of one of the rods is made into an eye and the end of the other rod is formed into a fork with an eye in each of the fork leg. The knuckle pin passes through both the eye hole and the fork holes and may be secured by means of a

collar and taper pin or spilt pin. The knuckle pin may be prevented from rotating in the fork by means of a small stop, pin, peg or snug. In order to get a better quality of joint, the sides of the fork and eye are machined, the hole is accurately drilled and pin turned. The material used for the joint may be steel or wrought iron.

Application :

1. Tie rod joint of roof truss.

2. Tension link in bridge structure.

3. Link of roller chain.

4. Tie rod joint of jib crane.

5. The knuckle joint is also used in tractor.

6. Elevators Chains

7. Valve Rods

8. Wire line tool-string

Dimensions of Various Parts of the Knuckle Joint

The dimensions of various parts of the knuckle joint are fixed by empirical relations as given below. It may be noted that all the parts should be made of the same material i.e. Mild steel or wrought iron.

If d is the diameter of rod, then diameter of pin, d1=d

Outer diameter of eye, d2=2d

Diameter of knuckle pin head and collar, d3=1.5d

Thickness of single eye or rod end, t =1.25d

Thickness of fork, t1=0.75d

Thickness of pin head, t2=0.5d other dimensions of the joint are shown in Fig. 1

The modes of failure: To minimize the failure of knuckle joint, the mode of failure and the stress induced must be studied.

1. Shear failure of pin (single shear).

2. Crushing of pin against rod.

3. Tensile failure of flat end bar.

Compressive stress and tensile stress, weakening of knuckle joint due to wear, plastic deformation due to overloading, and excessive thermal stresses are some of the other reasons for failure. Hence continuous use of knuckle joint may increase the magnitude of these stresses and ultimately result in failure of the knuckle joint.

Methodology of stress analysis

The virtual model similar to actual knuckle joint sample is created using CAD software. The stresses are obtained using the Finite Element Analysis is carried out. The results of finite element analysis are now verified with that of analytical method.

Finite Element Analysis (FEA)

The CAD Model is prepared in CATIA. The Finite element analysis carried out in ABAQUS. All steps are carried out to complete the analysis.

Data taken:

3D, solid, static problem

Material cast ASE 4340 forged steel

E = MPa,

Seed = 5, Element type- Quadratic tetrahedron

The model is meshed, Boundary conditions, loading applied.

Loading conditions

Load=1.5*106 N which is being applied as a pressure at the one side of the knuckle joint.

P=1.5*106/(π/4) d2

Where Diameter of the knuckle joint end d=50 mm

P=763.9~764 N/mm2

Boundary conditions

And at other end of knuckle joint is kept fixed for static analysis.

ENCASTRE: U1 =U2= U3 =UR1 =UR2 =UR3=0

RESULT:

Here we calculated stress by considering von mises and tresca criteria.

VON MISES CRITERIA

In von mises stress the maximum stress is acting at the fixed end and that is

= 1080 Mpa , = 0 Mpa

TRESCA CRITERIA: In tresca stress the maximum stress is acting at the fixed end is

= 1112 Mpa , = 0 Mpa

SPATIAL DISPLACEMENTS:

Displacement in x-direction

Displacement in y-direction

Displacement in z-direction

CONCLUSIONS

For reducing the failures of knuckle joint the estimation of stresses, their magnitudes and possible locations are very important.

To reduce the failure

Manufacturing process like Forging process should be preferred to the casting as the strength produced is more.

Removal of material is not preferred as it increases stress level, though reduces cost.

Grain refinement should be provided using suitable heat treatment process.

REFERENCES

R.S. KHURMI,book of “Machine design”, page no.134-139