Design and Performance Evaluation of Furrow Opener for Constructing Trapezoidal Shaped Furrow in Permanent Raised Bed Cropping Systems

摘要

Permanent Raised Beds (PRB) are systems where the crop and traffic zones (furrows)are clearly separated.In these system beds are constructed by piling up loose soil, usually from a tilled, flat surface, in such a manner that they regularly alternate with furrows.Recently PRB cropping systems, as a soil management systems, have been implemented in a wide range of irrigated and rainfed conditions.In the irrigated areas, one of the big drivers for using PRBs has been the concern over increasing levels of water scarcity, and hence the need to convert less efficient, traditional flood-irrigated systems to furrow irrigation based on PRBs; efficiency can be poor in the former systems especially when there is no access to laser leveling.Preliminary research on raised beds on P.R.China suggested that a 25-30％ saving in water is possible without yield loss for spring wheat.The conventional shape of the furrow in the PRB systems is the V-shaped furrow.Experience with PRB systems showed that the depth of the V-shaped furrow reduces with successive irrigations due to the earth slumping from the steep slope sides of that furrow.
　　The contribution of this research was to develop a furrow opener that could create a trapezoidal shaped furrow with moderately slope sides to alleviate the problem of earth slumping.The proposed furrow opener looks more or less similar to the conventional ones; with the big difference being the use of flat cutting share in a form of trapezoidal flat blade (TFB) instead of the conventional symmetrical wedge (SW) shaped cutting share.Therefore, the first step in the development of the furrow opener was to optimize the design of the TFB.The design of the TFB was optimized by the use of the finite element method (FEM); a recently available numerical technique that being used in the area of tillage tools design.A static three-dimensional nonlinear FEM model was developed, using ANSYS software, to investigate the effects of TFB geometry (bottom width and inclination angle) on the blade draft force, soil displacement field, and blade stresses.The mechanical behavior of the soil was simulated, based on the elastic-perfectly plastic theorem, by the use of Drucker-Prager (DP)model.Three sets of TFBs were tested all were having the same top width that equal to 150 mm,but varied in their bottom widths (W) which were set to be equal to 50, 75, and 100 mm.These blades were inclined to the horizontal by angles (R) of 20°, 25°, and 30°.The length of each set of the TFB depends on its inclination angle.
　　The combination of (W×R) gave a theoretical FEM experiment with nine treatments.Results of the FEM simulation showed that there is a direct relationship between blade draft force and the inclination angle, but the draft force of the blade increased with width in a less proportional relation.The least draft force was predicted for TFB that having 50 mm bottom width and 20° inclination angle (605.58 N).The maximum predicted draft force was for TFB that having 100 mm bottom width and inclined to the horizontal by 30° (748.58 N).Two sets of the TFBs that inclined to the horizontal by angles of 20°, and 30° were selected to be used as furrow opener flat cutting shares to validate the results of the FEM simulation.A prototype furrow opener was designed and developed.The proposed prototype was aimed to give a furrow with a fiat bottomed width and moderately slope sides.The performance of the furrow opener prototype was evaluated by Soil bin tests.In the soil bin experiments SW share was used with the furrow opener prototype just as a reference to compare the furrow opener forces; since in these experiments the only variable is the TFB geometry.During the soil bin experiments the working depth and speed were set constant at 200 mm and 0.1 m/s, respectively for all the tests.Results of the soil bin tests confirmed the predicted ones.
　　The least furrow opener force (9.52 KN) was measured for the furrow opener that used TFB with 50 mm bottom width and inclined to the horizontal by 20° angle.The maximum furrow opener force (10.73 KN) was measured for the furrow opener which used TFB with 100 mm bottom width and inclined to the horizontal by 30° angle.The measured furrow opener force when used SW as a cutting share was found to be 9.49 KN.The power requirements for the various geometry types of the furrow opener followed the same trend of the furrow opener forces; since the working speed was set to be constant.Although the least measured force of the furrow opener that used TFBs as cutting shares exceeded that of the furrow opener when used SW as cutting tillage point by 0.32％; but the ultimate aim is to have a furrow opener that could create a trapezoidal shaped furrow with slightly slope sides.The prototype furrow opener created a trapezoidal shaped furrow with bottomed width equal to 150 mm, top width of 600 mm, and depth of 200 mm.

目录

声明

LIST OF CONTENTS

LIST OF FIGURES

LIST OF TABLES

ABSTRACT

CHAPTER Ⅰ INTRODUCTION

CHAPTER Ⅱ LITERATURE REVIEW

2．1 Tillage and soil mechanics

2．2 Earth pressure theories

2．3 Classical soil mechanics and soil cutting

2．4 Analytical models

2．4．1 Limit equilibrium method(LEM)

2．4．2 Universal earthmoving equation

2．4．3 Payne model

2．4．4 O’cllaghan-Farrely model

2．4．5 Hettiaratchi-Reece model

2．4．6 Godwin-Spoor model

2．4．7 Mekyes-Ali model

2．4．8 Grisso et al．model

2．4．9 Weaknesses of analytical models

2．5 FEM models

2．5．1 Chi and Kushwaha model

2．5．2 Araya and Gao model

2．5．3 Mouazen and Nemenyi model

2．5．4 Fielke model

2．5．5 Jafari et al．model

CHAPTER Ⅲ SOIL DESCRIPTION AND PROPERTIES

3．1 Soil textural classiflcation

3．2 Soil bulk density

3．3 Soil moisture content

3．4 Mechanical properties of soil and soil-tool interface

3．4．1 Determination of soil shear strength properties

3．4．2 Determination of soil stiffness properties

3．4．3 Determination of soil-metal interface mechanical properties

CHAPTER Ⅳ FINITE ELEMENT METHOD SIMULATION

4．1 Theory of the Drucker-Prager elastic-perfectly plastic material model

4．2 Finite element formulation and virtual work

4．3 Building of the FEM model

4．3．1 Generation of soil-blade interface model geometry

4．3．2 Setting of the analysis type

4．3．3 Specification of the element type

4．3．4 Selection of units

4．3．5 Definition of material properties

4．3．6 Specifying the material model behavior

4．3．7 Meshing of the soil-blade interface model

4．3．8 Setting of the contact mechanism between blade and soil

4．3．9 Application of boundary conditions

4．4 Solution of the FEM model

4．4．1 Solution of material and geometrical non-linearities

4．5 Display of FEM model results

4．6 Results of the FEM simulation

4．6．1 Trapezoidal Flat Blade(TFB)draft force

4．6．2 Soil displacement field

4．6．3 Blade stresses

CHAPTER Ⅴ DESIGN AND DEVELOPMENT OF FURROW OPENER PROTOTYPE

5．1 Furrow opener prototype parts

5．1．1 Lower frog

5．1．2 Trapezoidal flat blade(TFB)

5．1．3 Upper frog

5．1．4 Moldboards

5．1．5 Furrow opener shank

CHAPTER Ⅵ SOIL BIN EXPERIMENTS

6．1 Soil bin description

6．2 Soil preparation

6．3 Experimentation

6．3．1 Tests procedure

6．3．2 Instrumentation

6．4 Soil bin experimental results

6．4．1 Furrow opener(tool)forces

CHAPTER Ⅶ CONCLUSIONS AND RECOMMENDATIONS

7．1 Conclusions

7．2 Recommendations and future perspectives

ACKNOWLEDGEMENTS

REFERENCES

APPENDIX A ANSYS SOFTWARE RUNNING PROCEDURE