**FEM ANALYSIS OF TILTING **

**MECHANISM OF THREE FURROWS **

**REVERSIBLE PLOUGH **

Anil R. Sahu

Department of Mechanical Engineering, B. D. College of Engineering, Sevagram, Wardha, Maharashtra, 442001, India

Prof. Dr. S. B. Jaju

Department of Mechanical Engineering, G. H. Raisoni College of Engineering, Nagpur, Maharashtra, India

Prof. N. K. Mandavgade

Department of Mechanical Engineering, G. H. Raisoni College of Engineering, Nagpur, Maharashtra, India

**Abstract: **

**In this paper the FEM analysis of manually operated tilting mechanism of three furrows reversible **
**plough is presented. Plough is important agricultural equipment used for soil preparation. The main **
**objective of this analysis was to optimize the design of tilting mechanism. The existing tilting mechanism **
**which is manufactured by local small scale manufacturer gets failed at different points after **
**approximately 150 Hr of uses. To analyze this tilting mechanism using FEM, firstly a proper CAD model **
**is developed using Pro/E cad software. Then by using ANSYs software FEM analysis is done to determine **
**the von Mises stresses. After carried out the analysis it has been found out that the existing design of the **
**mechanism is not proper and there is need to change in weld thickness, spring diameter and also the **
**material of the spring for efficient working and to withstand the different static and dynamic load. **

**Keywords: ****CAD, FEM, Agriculture tools, Tilting mechanism, Plough **

**1.** **Introduction **

In last few decades we all witnessed the development in each and every field. In the field of agricultural also we had seen remarkable development, big farmers are now a day’s using harvester, tractor, advance machine tools and advance farm equipments, but in the country like India where more than 80% of farmers are small and marginal and they are still doing farming by traditional method only they are also in need of improved agricultural tools that may be hand driven or bullock driven. The tools which they are required mostly manufactured in small scale industries or by local artisans like carpenter and blacksmiths. The present technique of manufacturing of agricultural tools by all these people is like design by evolution. The design is evaluate long span of time. The leisurely pace of technological change reduced the risk of making major errors. The circumstances rarely demanded analytical capabilities of the designer. Also this technique is unsuitable for mass production, difficult to modify, incapability to tap new technologies. The jobs made are not perfect, inefficient, health hazardous and very poor in quality in comparison to the parts made in big industry.

**2.** **Plough **

One of the most useful methods to avoid soil compaction is deep tillage by using a plough. Local plough (Hal) and blade harrow (Bakhar) are traditional implements used for loosening of soil. These are simplest tools designed to break the top soil and multi-passes are carried out to prepare seedbed. Mould board plough, disc plough, soil stirring plough, ridger plough, tool frames/carriers with mouldboard plough or tillage sweeps, etc. are improved implements designed for breaking soil.

**2.1.Types of plough **

(1) Reversible type of plough

The reversible plough has two moldboard ploughs mounted back-to-back, one turning to the right, the other to the left. While one is working the land, the other is carried upside-down in the air. At the end of each row, the paired ploughs are turned over, so the other can be used. This returns along the next furrow, again working the field in a consistent direction.

A reversible plough can be turned over by the tractor's hydraulics or manually at the end of the furrow and the next pass made against the previous strip. The ploughman drives backwards and forwards across the field until all is done.

(2) Non reversible type of plough

Non reversible plough can only turn the soil one way. If the ploughman were to run back alongside the previous furrow the soil would pile up in the middle. Instead the field is divided into lands. A land is an arbitrary area around which the ploughman drives in an elongated spiral. All the soil is turned the same way and there is only one slight ridge in the middle where the soil was turned together. As each land is finished and the next started there is a shallow trench left between the adjacent lands.

**3.** **Tilting mechanism of three furrow reversible plough **

The tilting mechanism is used to turned over the paired of ploughs which is mounted on the frame, at the end of the furrow.

Fig. 1. Tilting Mechanism

**4.** **Force calculation **

To calculate the different type of forces acting on different components of tilting mechanism, a free body diagram of tilting mechanism as shown in fig. no. 2 is developed. As the plough falls from a certain height, following two types of forces acts on the plough:

(1) Static load due to weight of the plough. (2) Dynamic load due to sudden impact of plough.

Fig 2. Free body diagram of tilting mechanism Let ‘u’ be the initial velocity of frame before falling, m/s

‘v’ be the final velocity of frame after impact, m/s

‘h’ be the height through which frame is falling as shown in above figure no. 3, m ‘g’ be the acceleration due to gravity, m/s2

‘a’ be the acceleration of the frame, m/s2 ‘s’ be the elongation of spring, m ‘m’ be the mass of frame, kg

Then initial velocity of frame is given by

*h*
*g*

*u* = 2* * _{ } _{(1) }

3 . 0 * 81 . 9 * 2 =

*u*

*u* = 2.4261 m/s
Now kinematical equation is given as follows

v2 = u2+2as (2)

v2 = (2.4261)2+2*a* 0.03

Here final velocity v = 0 after impact

0 = 5.885+0.06*a

A = -98.09 m/s2

(Negative sign indicates the retardation of the frame hence sign can be neglected) Now the force of impact (dynamic force) (F1) is given by

F1= ma (3)

F1= 350*98.09

F1= 34331.5 N

Now weight of body (F2) is given by following formula

F2 = m*g (4)

F2 = 350*9.81

F2 = 3433.5 N

Total force developed after impact (F) is equal to the sum of weight of body (F1) and force developed during

impact (F2).

F = F1 +F2

F = 34331.5+3433.5

F = 37.76 KN (5)

**5.** **Finite element analysis of tilting mechanism **

Finite element analysis (FEA) is a computer simulation technique used in engineering analysis, it uses a numerical technique called the finite element method (FEM). The finite element method (FEM) is one of the most used methods in engineering. These methods and programs based on it are fundamental usage in CAD. FEA / FEM are indispensable in all engineering analysis where high performance is required. The main purpose of the study is to see a practical application using FEA to improve design of a typical mechanical component. One of the major advantages of FEM is the simplicity of its basic concepts. To perform a finite element analysis, the user must develop a calculus model of the analyzed structure. There are no algorithms and general methods for developing a unique model that approximate, with a known error, the real structure. The development of structure of a model is based on the intuition experience and imagination of the user.

Each model consists of lines, planes or curved surfaces and volumes, created in a 3D CAD environment. In this stage of development, the model is continuous with an infinite number of points like the real structure. The main goal of FEM is to obtain the finite element mesh, transforming the continuous structure into a discrete model, model with a finite no of points. The boundary condition and external loads are applied to this system before solving. The result of the solution is available at the nodes of the elements. Finite element analysis can display them in graphical form to analyse them, to make design decisions and recommendations.

Conventional analytical method for solving stress and strain become very complex and almost impossible when part geometry is very complex and almost impossible when part geometry is intricate. In such cases finite element modelling becomes very convenient means to carry out the analysis. Finite element process allow discretising the intricate geometries into small fundamental volumes called finite element. It is possible to write the governing equations and material properties for these elements. These elements are then assembled by taking proper care of constraints and loading, which result in set of equations .these equations when solved give the result that described the behaviour of original complex body being analysed.

**5.1.**** Modeling of Tilting Mechanism **

A solid model of tilting mechanism is generated using Pro/E software. As shown in fig. 3

Fig. 3. Solid model of tilting mechanism

**5.2.****Setting the type of analysis to be used: **

With the ANYSs software it is possible to perform different type of analysis like. Structural, fluid, thermal, electromagnetic etc. in this case structural type of analysis is used.

**5.3.****Specify element type and constants: **

**5.4.****Meshing **

Meshing is the integral part of computer - aided engineering (CAE) analysis process. The mesh influences the accuracy, convergence and speed of solution. Furthermore, the time it takes to get result from a CAE solution. Therefore, the better and more automated the meshing tools of ANSYS software which having smart size option is to control size of element and nodes. Smart element sizing (Smart Sizing) is a meshing feature that creates initial element sizes for free meshing operations. Smart Sizing gives the mesher a better chance of creating reasonably shaped elements during automatic mesh generation. This feature, which is controlled by the SMRTSIZE command, provides a range of settings (from coarse to fine mesh).

Fig. 4. Meshed model of tilting mechanism along with assembly

**5.5.****Specify material properties **

**5.6.****Boundary and loading condition **

Finite element analysis is to examine how the structure or components responds to different loading conditions. Specifying the proper loading condition is therefore, a key step in the analysis. The word loads in ANSys terminology includes boundary conditions and externally or internally applied forcing functions.

Different forces applied to the tilting mechanism

1. Vertical component of total Force (calculated in section 3 from equation no 5) i.e. Fsinθ = 26160N will be applied to spring

2. Total Force i.e F = 37.76 KN is applied on the connecting rod. Table 2. Boundary and loading condition

Fig. 5. Different loading on assembly

**5.7.**** Stress Analysis Result **

Table 3 Stress Analysis Result

Name Figure Minimum Maximum

Equivalent stress (Von-Mises )

6 2.7356e-003Pa 8.298e+008Pa

Shear stress 7 1.5776e-003Pa 4.5152e+008Pa

Fig. 6. Equivalent stress (Von-Mises ) Fig. 7. Shear stress

Fig. 8. Total deformation

It has been observed by doing FEM analysis of assembly of three furrow reversible plough that maximum stress is concentrating on the weld joint only, and on all other part there is very minimum or no stress concentration is observed. Hence separate analysis of weld joint and spring is carried out.

**6.** **Analysis of spring of existing model **

As it is reported by the manufacturer the spring is getting fail, and also by FEM analysis of assembly it has been observed maximum stress concentration is developed on the joints, we had separately analyze the spring. In the existing model material of spring is used, oil tempered stainless steel (SAE 1070-1090) having allowable stress value =420 N/mm2, spring wire diameter = 3mm and outer diameter of spring = 30mm.

**6.1.FEM analysis of spring **

From the FEM analysis of spring (figure 10) it has been observed that maximum von-Mises stress is developed on the spring = 1.7886e11 Pa is quite high than the allowable stress 420 N/mm2 hence spring is getting failed. To overcome this failure we had redesigned the spring.

Fig 10. Equivalent stress (Von-Mises ) of existing Spring

**7.** ** Analytical design of spring and weld **

**7.1.** **Design of spring **

As the existing spring is getting failed in this section we redesigned or modify the spring. Design of spring may be modified either by increasing wire diameter or by changing the outer diameter of the coil using same material or by using new material.

Design of spring by using same material and same outer diameter of spring is same (because of space constraint).

Let σ be the stress induced in spring,

Dm be the mean diameter of the spring, mm

d be the diameter of the wire, mm σ =(8*F*Dm)/( ∏*d^3) 420=8*26700*30/(∏*d^3) d=16mm

the wire diameter of spring is comes out to be 16 mm. Since this value is more than permissible value, so we have to change the material of the spring having high shear stress.

Spring is redesigned by using improved spring material i. e. by taking music wire whose shear stress equal to 1060 Mpa.

Stress induced in the spring is given by following formula

σ =

3 ^ 8

*d*
*FDm*
*K*

Π (6)

Where,

Wahl’s factor K =

*c*
*c*

*C* 0.615

4 4

1 4

+ −

−

Again C (spring index) =
*d*
*Dm*

Now by putting all values in equation 6, we get

1060=(8*26.7*10^3*Dm)/ (∏*d^3)

Dm/d^3=0.0155

If Dm=30mm,

Then d=8.2mm

Now,

σ= (8*26.7*10^3*30)/ (∏*8.2^3)

=3.7 *10^3 N/mm2

Now spring index,

c=
*d*
*Dm*
=
2
.
8
30
= 3.65

Now with this spring index we have to calculate stress which is given as follows

σ =
3
^
8
*d*
*FDm*
*K*
Π
σ =
3
^
2
.
8
*
30
*
3
^
10
*
7
.
26
*
8
*
65
.
3
Π

=13.53*103 N/mm2

With this dimension of the spring we get safer design of spring, hence we suggest that mean diameter of coil (Dm) should be 30mm and diameter of wire (d) should be 8.2mm so as to withstand the force of impact.

**7.2. DESIGN OF WELDING **

The stress on welded joints are difficult to determine because of variable and unpredictable parameters like homogeneity of the weld metal, thermal stresses in the welds, changes of physical properties due to high rate of cooling etc. the stresses are obtained, on the following assumption;

1. The load is distributed uniformly along the entire length of weld 2. The stress is spread uniformly over its effective section. Load acting (p) on Fillet joint

P= ∏*D*t*σt (7)

Where

D is the mean diameter of the coil=30 mm

σt is the maximum tensile stress of the weld in our case = 25 Mpa (for carbon steel AWS E6013)

By putting all above values in equation no.7 we get

26.7*10^3=∏*30*0.707*12* σt

σt=33.39 N/mm2

But allowable shear stress for the material (for welding carbon steel AWS E6013 = 25 N/mm2) Therefore weld is not safe.

So we have to redesign the weld.

σt= p/A

By putting all above values we get,

25=26.7*10^3/A

A = 1068 mm2 But,

A = ∏*D*t

1068=∏*30*t

Therefore,

t=11.33 mm

t=0.707*s=11.33

Therefore,

S=16.025 mm

Therefore we suggest thickness of the fillet weld = 11.33 mm and size of the weld =16.

**8.** **FEM analysis of modified spring and weld **

Stress Analysis Result

Table 4 Stress Analysis Result of modified spring and weld

Name Figure Minimum Maximum

Shear stress 11 65038Pa 7.7087e9Pa

Equivalent stress (Von-Mises ) 12 1.2765e5Pa 1.3439e10Pa

Fig. 11. Shear stress Fig. 12. Equivalent stress

**9.** **Result and discussion **

From all the observations and based on the analytical and FEM analysis it has been observed that spring and welding of tilting mechanism gets failed due to force which is acting on tilting mechanism. Stress which is developed because of impact load of plough is 1.7886e11Pa quite high than the allowable stress 420 N/mm2 hence spring is getting failed. It is also observed in the present tilting mechanism the thickness of welding is not sufficient to withstand the impact load the stress developed on the weld is 33.39 N/mm2 , But allowable shear stress for the material (for welding carbon steel AWS E6013) = 25 N/mm2. Therefore weld is not safe. From the FEM analysis of assembly of three furrow plough it has been observed that all the other parts of the assembly are safe only maximum stress is developing on the joint parts.

Hence we redesigned the spring by using music wire, keeping outer diameter of coil constant i.e. 30mm (because of space constraint) we got new wire diameter = 8mm this dimension is quit high then the existing wire diameter = 3mm. But due to increase in wire diameter the contact area of spring is also increases and also the thickness of the weld is increases from 8mm to 11mm.

After doing the FEM analysis on modified spring and weld design it is clearly observed that, maximum stress induced on the assembly is less than the allowable stress therefore the new modified design of spring and weld is safe. Also there is no maximum stress concentration on the weld and on any region of spring, hence new design is safe.

**10.Conclusion **

The structural static analysis of tilting mechanism of three furrow plough is carried out to find out the different failure in the mechanism due to different loading condition. By FEM analysis the value of stress found to be more at different joints and on the spring as indicated by red colour. Hence possibility of failure is high at these section compared to other section of assembly. Accordingly we redesign the spring and welding. By using CAD modelling and performing FEM analysis by using ANSYS software it is possible to analyse correctly different type of stress which is going too developed on the product with different loading condition, hence we get optimal design of the product.

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