Design of a partially parallel stump jump mechanism using computer-aided design

2.r. r, nB

Design of a partialty Parallel Stump Jump M

usrng

Computer -Aided Design

B.B.S Lutchmeea

Thesis Submitted for the degree

Master of Applied Science

The University of Adelaide Australia

(Faculty of

Agricultural

and Natural Resource Science)

by

of

IN

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iv4ay 1997

TABLE OF CONTENTS

Table of Figures

List

of Tables Acknowledgments Declaration Abstract

1. LITERATURE REVIEW

1.

I

Stump-jump mechanism 1.2 Historical background

1.3 Cunent stump-jumP mechanism 1.3.1

Coil

type stump-jurnP 1.3.2 Cushion spring ^tYPe.

I.3.2.I

Forward-mounted cushion spring 1.3.2.2 Rear-mounted cushion ^{sprin g} 1.3.3 Lock toggle tyPe

1.3.4 Hydraulic type

1.4 Past research on stump-jump mechanism 1.5 Forces acting on the stump-jump mechanism 1.6 Computer Aided Design

(CAD)

1.6. 1 Kinematic synthesis/analysis of mechanism

1.6.2 Computer-Aided ^design of spring loaded mechanism 1.6.3 Rigid body motion/Finiæ element analysis

1.7 Desirable features of a stump-jump mechanism

1.8 Factors alt'ecting the design of stump-

jump

mechanism

1. 8. 1 Desirable characteristics of stump-ìump mechanisms 1.8.1.1

Avoid

excess storage of energy

1.8.I.2

Setting of _Pre-load 1.8.1.3 Re-entrY of tine into soil

2. KINEMATIC DESIGN OF THE MECHANISM 2.l lntroduction

2.2 Desirable kinematic specifications of the mechanism 2.3 Kinematic Design of the mechanism

2.3.lThe

approach via the computer package 2.3.2 Procedure fbr kinematic design

lv

iv vi

vü

4

4 4

-5 -5

6 6 6 7 tì

9

13

2T

22 22 22 22 22

23

23 26

l5

16

t7 l8

26 26 27

2.4 Results

2t

2.5 Discussion and Conclusions

3. KINETIC ANALYSIS OF THE MECHANISM

3.1 Introduction

3.2 Assumptions made fbr force analysis of the mechanism 3.3 Force analysis of the mechanism.

3.3.1 General Description of

MICRO-MECH

3.3. 1. 1 Executive module 3.3.I.2 Model definition ^module 3.3.1.3 Modet modification module 3.3.I.4 Mechanism analysis module 3.3. 1.5 Mechanism animation module 3.3.1.6 Report generation module

3.4INPUT DATA

^{FOR FORCE}

ANALYSIS

3.4.1

Definition

of the kinematic topology 3.4.2

Link

length /dimensions

3.4.3 Gravity vector

3.4.4 Centre

of

gravity, Polar ^mass moment of inertia, weight of

link

3.4.5

Definition

^{of points.}

3.4.6

Definiúon

of the known tbrces 3.4.7

Detinition

of the unknown tbrces

3.4.8 Specification of the independent

joint

elements 3.4.9 Solution control ^parameters

3.5 Results of tbrce analysis 3.5.1 Forces

At

Joint J1

3.5.1.1 Forces

At

Joint J2 3.5.1.2 Forces

At

Joint J3 3.5.1.3 Forces

At

Joint J4 3.5.I.4 Acceleration

Of

Point P9 3.5.1.5 Acceleration

Of

Point P10 3.-5.1.6 Acceleration

Of

Point

Pl1

3.5.1.7 Unknown Force

4. DESIGN OF THE MECHANISM FOR STRENGTH

4.1 Introduction

4.1.1 Finite element method

4.I.2

General description of the tiniæ element method and ^steps of tìnite element analysis

4.1.3 Steps of

tinite

element analysis 4.1.3.1 Discretise( model) the structure 4.1.3.2 Define the element properties

4.I.3.3

Assemble the element stit'fness matrices.

4.1.3.4

Apply

the loads

4.1.3.5

Defrnition'of

boundary conditions.

ll

32

35

35

36 39 39 40 40 40 40

4I 4l

42 42 42 43 43 44 45 46 46 46 4tì 48 49

-50 51 52 53 54

5-s

56

-56

56 57 57 57 .58

5tì 58

-58

4.1.3.6 Solving the system of linear algebraic equations

4.t.3.7

Calculation of ^stresses

4.2Fniæelement

^{analysis of} the mechanism

4.2.1 Procedure for Finite element analysis of the mechanism 4.3 Structural Design of the driver

link

4.3.1 Stress analysis using

tinite

element method

4.3.I.1Results

^{of the driver}

link

4.3.2Fatigue analysis of the driver

link

using Soderberg criteria 4.4 Structural design of the coupler

link

4.4.1 Finiæ element analysis of the coupler

link

4.4.2Fattgue analysis of the coupler

link

4.5 Structural design of the

follower link

4.5.1 Finite element analysis of the

tbllower link

4.5.2 Fatigue analysis of tbllower

link

5. GENERAL CONCLUSIONS REFERENCES

APPENDIX I

^(a) Diagram of the detail of the

joint

and tine at rest (b) Diagram

of

the eftects

of

striking an obstruction

AppENDIX 2

Input listing tbr the

tinite

element analysis of the driver

link AppENDIX 3

Input listing for the

tinite

element analysis of the f-ollower

link

59 60 59

.s9

66 66 67 69 69 69

1l

72 72 72

74

77 80 82 15

1

Table of Figures

FIGURE I-IFORWARD MOUNTED CUSHION SPRING FIGURE 1-2 REAR MOUNTED CUSHION ^SPRING FIGURE 1-3 LOCKTOGGLE

FIGURE 14 HYDRAULIC TYPE

FIGURE 2-1 EXISTING STUMP-JUMP MECHANISM

FIGURE 2-2 POSITION OFEXISTNG ^FOUR BARLINKAGE

FIGURE 2.3 VERTICAL DISPLACEMENT V/S ROTATION OF TTIE TRACER POINT P FIGURE 2-4 VERTICAL DISPLACEMENT V/S HORZONTAL DISPLACEMENT OF T}IE

TRACER POINT P

FIGURE 2-5 POSITION OF THE MECHAMSM

FIGLIRE 2-6 DISPLACEMENT

IN

Y V/S DISPLACEMENT IN X OF TRACER POINT FIGURE 2-7 DISPLACEMENT IN Y ^V/S ROTATION ^OF THE TRACER POINT P2 FIGURE 3-1 FREE BODY DIAGRAM OF THE MECFIAMSM

FIGURE 3-2{and3-28

FIGURE 3-3

FIGURE 3-4 ARCHITECTURE OFMICRO-MECH (FROM MICRO-MECH MANIIAL) FIGLIRE 3-.5 POSITION OF POINTS ON T}IE MECHAMSM

FIGURE 4.1 ANSYS PROGRAM ORGANISATION FTGURE4-2 DRTVERLINK

FIGURE 4-3 COUPLER LINK FIGURE 4-4.FOLLOIWER LINK

FIGURE4-s FINITE ELEMENT MODEL OF DRIVER LINK FIGURE4-6 FINITE ELEMENT MODEL ^OF COUPLERLINK FIGURE 4-7 FINITE ELEMENT MODEL OF FOLLOWER LINK FIGI]RE4-8 STRESS CONTOURS OFT}IE DRTVERLINK

FIGURE 4-9 STRESS CONTOI]RS AT THE JUNCTION OF THE LINK AND THE TINE FIGTIRE 4-10 STRESS CONTOURS OF THE LINK AND TINE

FIGURE 4-1 1 STRESS CONTOURS OF THE FOLLOIWER LINK

List of Tables

TABLE 2-1 DIMENSION OF TTIE EXISTING FOUR BAR LINKAGE TABLE 2-2 DIMENSION OF T}IE FOUR BARLINKAGE

TABLE 2-3 KINEMATICS ^{OF THE FOUR-BAR} LINKAGE TABLE 3-IDIMENSION ^OF TIIE LINKS

TABLE 3-2

TABLE 3-3 POSITION OF POINTS ON THE IVTECHANISM TABLE 3-4 FORCES AT JOINT ¹

TABLE 3-5 FORCES AT JOINT J2

TABLE 3-6 FORCES AT JOINT J3

TABLE 3-7 FORCES AT JOINT J4

TABLE 3-8 ACCELERATION OF POINT P9

TABLE 3-9 ACCELERATION OF POINT PlO TABLE ^3-10 ACCELERATION OF POINT

Pll

TABLE 3-11 UNKNOWN ^FORCE AT POINT Pl

6 7 8 9

23 24 25

25 28 33

-t-1

36 37 31 40 47

60

6l

62 62 6?

64

ó-5

68 70

7l

7?

24 28 29

42

M

45 48 49 50

5l

52

.53

54

.5-5

lv

Acknowledgements

I

graæf'ully acknowledge the assistance, guidance and encouragement

of

^my supervisor.s

Hugh

Reimers and

Paul Harris of the Faculty of Agricultural and Natural

Re'source Sciences, The University of Adelaide and

Dr.

Kazeem Abharry and

Dr.

John Fielke

fiom

the School of Manutäcturing and Mechanical Engineering, The Levels

Campus,

University of

South Australia.

The completion of this

research

would not

have been possible

without

their guidance and assistance

in

particular

Dr.

Kazem Abhary

who

wa.s

actively involved in the design part of the project.

I

would also like

to

thank

Dr.

J.

M.

Desbiolles and Andrew Burge

tiom

the

Agricultural

aml Machinery Research ^and Design Center,School of Manutäcturing and Mochanical Engineering,

The Levels, University of South Australia tbr their help, advice

ancl triendship.

Special thanks are due

to

Professor David Coventry, Head

of

the Department and David

Matthew, Acting

Departmental

Manager tbr providing administrative and

fìnancial support.

It

was my pleasure to be

with

them during my stay.

Finally my deep appreciation ^goes to my täther who provided me

with

moral support and encouragement throughout the period of study

v

Declaration

This work

^contains

no

^material

which

has been accepted t'or

the award of

any other clegree

or

diploma

in

any university

or

other

tertiary institution

^ancl,

ttl

the best

of

my knowledge and beliet', contains

no

material previously published

or written by

another person, except where due retèrence ^has been made in the text.

I

give consent to this copy of my thesis, when deposited in the University Library, ^being available

tbr

loan and photocopyrng.

Signed

Date ?á-rj A?-

B.B.S. Lutchmeea

vr

Thesis

Design of partially parallell stump-jump mechanism using computer-aided design

Abstract

Change in tillage practice over the ^past decade has been greatly influenced by

two

tãctors namely the need

to

reduce energy consumption

in

tillage operations and the retention

of crop

residue

as a soil

conservation measure. These changing

cultural

practices have greatly intluenced tillage

tool

design. One response

to

these changes involves the design

of

a partially-parallel stump mechanism

to

cope

with

the new conditions.

In

this research computer aided design

is

used

to

improve the design

of

a

partially

parallel stump jump mechanism

which

was

initially

developed

by Riley. The principal aim is to

reduce the existing

link

dimensions

of the

mechanism

so that it

can

be

.suitable

tbr

use

on

small tractors.

To

achieve the above aim, kinematic analysis was pertbrmed by using the

LINCAGES-4

computer sottware package

tbr

sizing

of the links. The

mschanism

was

de.signed

tbr

chisel ploughing

tbr

tluctuating load

with

average horizontal antl

vertical soil

tbrces

of 2.5 kN and 1.0 kN

respectively.

Force

analysis

was carried out using the MICRO- MECH

sotiware package

tbr

calculation of

joint

tbrces. For the stress calculation impact and

tätigue

phenomena

were

taken

into

consideration and

a

separate computer-aided tìniæ element analysis was pertbrmed

on

individual

links of the

mechanism.

The

result obtained

tiom the kinematic

analysis

shows that there was an

improvement

in

the dimensions

of

the links. The driver

link

has been reduced

tiom

600 mm

to

363 mm, the coupler

link

from 400 mm to 303 mm and the

tbllower link fiom

400 mm to 306 mm.

vu