STUDY OF THE STATIC STRUCTURAL ANALYSIS OF THE MONO ... · effectiveness of a Mono crankshaft in meeting the intent of the design. A finite element model was created as the first

DOI:10.23883/IJRTER.2018.4343.ZM2N6 246

STUDY OF THE STATIC STRUCTURAL ANALYSIS OF THE

MONO CRANKSHAFT FOR BENDING AND TORSIONAL LOADS

Yashwanth.L1,Lohitesh Jaga Kumar2

1,2Dept.of Mechanical Engineering, Akshaya Institute of Technology, Tumkur, Karnataka

Abstract- In this paper deals with application of Finite Element Analysis for determining the

effectiveness of a Mono crankshaft in meeting the intent of the design. A finite element model was

created as the first step. Then a Finite Element Analysis of the Mono crankshaft was performed,

including a static analysis and since the crankshaft experiences dynamic loads, a Free-Free modal

analysis is performed. Appropriate elements size, boundary condition and loading conditions were

applied on the FE model.

Using Mass Beam element, a mathematical model was created for the free-free modal

analysis. The analysis was validated through mathematical hand calculations. Hypermesh is used as a

Pre-processors for meshing and generating Finite Element Model. ANSYS 10 has been used as a

Solver and Postprocessor for the Analysis and the interpretation of results.

The analysis is carried out to assess the strength and stiffness of the crankshaft using the CAE

tools. The results of Finite Element Analysis and the mathematical calculations are as discussed.

Keywords- Crank shaft, Modeling, FEM Analysis

I. INTRODUCTION

The main driving shaft of an engine that receives reciprocating motion from the pistons and

converts it to rotary motion. Together, the crankshaft and the connecting rod transform the piston

reciprocating motion into rotary motion.

A crankshaft, in general, converts linear motion into rotary motion. In an internal Combustion

engine, the reciprocating motion of the piston is linear and is converted into rotary motion through

the crankshaft. [1]

II. LITERATURE REVIEW

Earlier researchers had studied and published on design and analysis of crankshaft Listed below is

those important works.

R. G. Desavale et al.[1] on ‘’Theoretical and Experimental Analysis of Torsional and Bending Effect

on Four Cylinders Engine Crankshafts by Using Finite Element Approach’’

The issue of torsional vibration of the crankshaft of rapid diesel motor has turned out to be basic with

increment in excitation powers. This outcomes in high torsional vibration amplitudes and henceforth

high burdens the paper goes for finish FEM examination of a crankshaft for torsional and bowing

vibrations, recognizable proof of stresses. It is examined for regular recurrence, inflexible body mode

shape by ANSYS and Holzer strategy. The total reenactment of genuine limit conditions is improved

the situation diary bearing help, latency lumping for responding parts and bearing firmness. Modified

code is created in ANSYS-Macros, which will change over client input Pressure-Crank point variety

to excitation powers for different requests through FFT. The dynamic reactions got for dislodging

and stresses. At long last all outcomes are consolidated to get the variety of Filet Stress as a

International Journal of Recent Trends in Engineering & Research (IJRTER)

Volume 04, Issue 06; June - 2018 [ISSN: 2455-1457]

@IJRTER-2018, All Rights Reserved 247

component of motor speed and symphonious requests. The basic dynamic reaction is contrasted and

comes about got tentatively for torsional amplitudes

Farzin H. Montazersadgh et al[2]. on ‘’Dynamic Load and Stress Analysis of a Crankshaft’’

In this examination a dynamic recreation was directed on a crankshaft from a solitary chamber four

stroke motor. Limited component investigation was performed to get the variety of stress size at

basic areas. The weight volume graph was utilized to compute the heap limit condition in unique

reenactment show, and other recreation inputs were taken from the motor detail diagram. The

dynamic investigation was done diagnostically and was checked by recreation in ADAMS which

brought about the heap range connected to wrench stick bearing. This heap was connected to the FE

show in ABAQUS, and limit conditions were connected by the motor mounting conditions. The

examination was improved the situation distinctive motor paces and subsequently basic motor speed

and basic district on the crankshaft were gotten. Stress variety over the motor cycle and the impact of

torsional stack in the examination were researched. Results from FE examination were checked by

strain gages joined to a few areas on the crankshaft. Results accomplished from previously

mentioned investigation can be utilized as a part of weakness life count and streamlining of this

segment.

Lohitesh Jaga Kumar, Praveen D.N, R.Thara, Irfan G et al [3]. on “Experimental & Finite Element

Analysis of Sisal Fiber Reinforced Composites” In this paper a Polymer matrix composites

reinforced with Synthetic fibers such as glass, carbon, aramid,etc. though they are expensive these

are being used in various application since they favourable mechanical properties. Nowadays natural

occurring fibers such as sisal, flax, hemp, jute, coir, bamboo,banana, etc. are widely used for

environmental concern over synthetic fibers. Engineered bio-composites are needed to meet the

needs of users for construction and commodity products which will simultaneously maximize the

sustainability of natural resources. These engineered bio-composites are opening new markets in the

field of commercial construction, automotive, aerospace and also reducing effects on the

environment such as energy, air, water, and waste.

III. PROBLEM DEFINITION

The principle driving shaft of a motor that gets responding movement from the cylinders and

proselytes it to turning movement. Together, the crankshaft and the associating bar change the

cylinder responding movement into revolving movement.

A crankshaft, when all is said in done, changes over straight movement into rotational movement. In

an interior Combustion motor, the responding movement of the cylinder is direct and is changed over

into revolving movement through the crankshaft.

IV. AIM OF THE PROJECT

The aim of this research is to design, analyze and validate and to assess and compare the

Analytical results with the software results of forged steel for a structural analysis and Modal

analysis results using HYPERMESH & ANSYS Tools

V. GEOMETRICAL MODELING

In this chapter geometric modeling, design assumption, material properties considered is as discussed

below:

Crankshaft is a focal segment of any interior ignition motor and is utilized to change over responding

movement of the cylinder into rotatory movement or the other way around. Crankshafts come in

numerous shapes and sizes from little ones found in two-stroke little motors to mammoth ones found

in diesel motors in ships. Crankshafts in car motors likewise differ every one special to its motor




kind and make. The crankshaft primary diaries pivot in an arrangement of supporting orientation

("fundamental direction"), causing the counterbalance pole diaries to turn in a roundabout way

around the principle diary focuses, the width of which is double the balance of the bar diaries. The

measurement of that way is the motor "stroke": the separation the cylinder climbs and down in its

barrel. The huge closures of the associating bars ("conrods") contain orientation ("bar heading")

which ride on the counter balance pole diaries.

Exchanges with different perceived specialists in the crankshaft field make it inexhaustibly certain

that there is no „right‟ reply, and suppositions about the needs of plan criteria shift impressively. In

contemporary dashing crankshaft plan, the prerequisites for twisting and torsional firmness contend

with the requirement for low mass snapshot of inactivity (MMOI). A few crankshaft specialists

underscored the way that fascinating metallurgy is not a viable replacement for appropriate outline,

and there's little point in changing to exotics if there is no weariness issue to be comprehended.

High solidness is an advantage since it expands the torsional full recurrence of the crankshaft, and in

light of the fact that it diminishes twisting avoidance of the bearing diaries. Diary avoidance can

cause expanded erosion by irritating the hydrodynamic film at basic focuses, and can cause loss of

oil in light of expanded spillage through the more noteworthy spiral clearances that happen when a

diary's hub isn't parallel to the bearing axis.

3.1 Geometric Modelling of Mono-Crankshaft

The modeling is finished utilizing Catia with the assistance of standard measurements that we got

past the watchful audit. The Catia is one of the celebrated displaying programming accessible in the

market which empowers us not exclusively to do the demonstrating of the parts yet in addition the

examination of the same. Consequently it is one of the perfect programming for demonstrating and

investigation issues. The accompanying outline is the model of the Mono Crankshaft which is made

utilizing the Catia Software.

Figure1: Mono Crankshaft Geometric Model

VI . MATERIAL PROPERTY DETAILS The material properties used for the Sheet metal and its mechanical properties is as shown below:

Medium-carbon steel compounds are made out of dominatingly the component press, and contain a

little level of carbon (0.25% to 0.45%, portrayed as„25 to 45 points‟ of carbon), alongside mixes of a




few alloying components, the blend of which has been deliberately outlined so as to create particular

characteristics in the objective composite, including hardenability, nitridability, surface and center

hardness, extreme rigidity, yield quality, continuance limit(fatigue quality), malleability, affect

protection, consumption protection, and temper-embrittlement protection. The alloying components

ordinarily utilized as a part of these carbon steels are manganese, chromium, molybdenum, nickel,

silicon, cobalt, vanadium, and infrequently aluminum and titanium. Every one of those components

includes particular properties in a given material. The carbon content is the fundamental determinant

of a definitive quality and hardness to which such a compound can be warm treated.

In changing over the straight movement of the cylinder into rotational movement, crankshafts work

under high loads and require high quality. Crankshafts require the accompanying attributes

High quality and solidness to withstand the high loads in present day motors, and to offer

open doors for cutting back and weight lessening

Resistance to weakness in torsion and bowing

Low vibration

Resistance to wear in the bearing territories.

Along these lines the fashioned steel crankshafts offer higher quality and firmness and the other

material attributes than the cast press elective

Sl No Component Material Young’s

Modulus

Poisson’s

Ratio

Yield

strength

1 Crankshaft Steel 2.1e5 MPa 0.3 250 MPa

Table 1: Material Properties for the Crankshaft

VII FINITE ELEMENT MODELING In this chapter a geometric model is converted into a Finite Element Model, selection of element

type, assumption of loading and boundary condition are discussed as below:

The finite element is a mathematical method for solving ordinary & partial differential equations,

because of its numerical method it has an ability to solve complex problems which are represented in

the form of differential equation. These types of equations occur naturally in all fields of the physical

science & application wise it is limitless as concern the solution of practical design problems.

Commonly FEA is described as a discretization technique.

Figure 2: Geometric Model of the Mono crankshaft




To develop a finite element model, it involves certain steps & mesh requirement as mentioned

below:

Characterizing the geometric space of the issue.

1. Defining the component connectivity‟s (work the model).

2. Defining the component compose to be utilized.

3. Defining the material properties of the components.

4. Defining the geometric properties of the components (length, zone, and so forth).

5. Defining the physical limitations (limit conditions).

6. Defining the loadings.

7.1 Defining the element connectivity’s (meshing the model)

Basically geometry have a various entities like point, lines, curves, areas, surfaces, volume &

solids. But in the FEA we have only two entities i.e, nodes & elements. FEA entities are build with

respect to the geometric entities & for the simulation only FEA entities are considered.

Finite element modeling of the crankshaft is done in the Hypermesh 7.0 software. And the mesh

model of the crankshaft is as shown in the figure.3.

Figure 3.: Finite Element model of a mono crankshaft

7.2 Defining the element type used for the meshing: Type of element used is SOLID185:

1. It is 3D 8 node structural solid.

2. It is having three degree of freedom system in each node translations in x, y and z direction.

3. This element has a stress stiffening and large deflection and plasticity and large strain

capabilities.

4. Linear hexahedron elements with special formulation like the use of extra shape functions and

reduced integration result in solutions that are very accurate.

5. It also has mixed formulation capability for simulating deformation of incompressible

elastoplastic materials.

7.3 Justification for consideration of Solid 185 element is as mentioned below: 1. In this element the pressure may be applied as a surface load, where as in other elements it is not

possible.

2. Compare to tetrahedral element, It has mixed formulation capability for simulating deformation

of nearly incompressible elastoplastic materials and fully incompressible hyper elastic materials.




3. Linear Hexahedron elements result in fewer degrees of freedom when compared to the Quadratic

Tetrahedron elements. Thus it require less CPU and disk storage.

4. Hence Hexahedron elements give better results when compared to Tetra/Wedge/Pyramid

elements.

7.4 Defining the order of an elements: There are two type of order:

First order elements: For linear elements the edge is defined by a linear function called shape function whose degree is

one or first order elements.

Second order elements: For elements having mid side nodes on the edge quadratic function called shape function whose

degree is two is used, hence it is called as second order or Quadratic element. Similarly elements

having more nodes on the edges are defined as higher order or higher degree elements.

Basically first order elements have been selected for the mono-crankshaft, because higher order

elements when over lapped on geometry can represent, complex shapes very well within few

elements. And the solution accuracy is more with the higher order elements. But with higher order

elements the computational effort required is more. Hence first order element is considered for the

Crankshaft finite element model.

7.5 Defining the Size of an element: FE method is based on the calculated approach; the solution can‟t be as exact as the analytic result.

So the precision of an analysis mainly depends on the size and position of the elements, element type

& also on the element formulation.[5]

1. The size of an element directly depends upon the mesh requirement:

2. The mesh must be valid.

3. The work must comply with the limit of the area.

4. The thickness of the work must be controllable, to permit exchange off amongst precision and

arrangement time.

5. The matrix thickness will fluctuate contingent upon neighborhood exactness prerequisites,

however any varieties must be smooth to decrease or kill numerical dissemination/refraction

impacts.

6. Even it relies upon the state of a component.

By considering the above points, into the finite element modeling of the crankshaft, the global

element size is considered as 1mm. and the local element size varies from 0.5mm to 1mm. To

determine the quality of results even mesh parameters are also considered into the FE Model as

shown in the table2.




Table 2. : Quality Matrix for the 3D solid elements

To justify this a supplementary analysis is done on the round bar of the similar given crank pin

diameter size i.e, as shown in the figure4, where the actual load is going to act, by increasing the

element size from 1.5mm to 0.5mm with increase in the density of the mesh, a static structural

analysis is carried out and the obtained results are plotted in the form of Stress Vs number of

elements as shown in the graph1.

Figure 4: FE Model of the round bar for supplementary analysis




Graph 1 : Number of element Vs stress obtained

From the above graph2. we can see that as the number of element increases the stress will also

increases, at a particular element size the stress value does not vary in large unit hence we consider

this element size for the analysis.

7.6 Defining the physical constraint ( Boundary Conditions):

For the given crankshaft in light of its working standard. The mounting of the given crankshaft is on

two unique heading which brings about various limitations in the limit conditions. Under the stacked

condition one side of the mono crankshaft is settled to the motor square by a metal roller and the

opposite side by moving over the diary bearing.

Idealization made for the boundary conditions: 1. When the crankshaft is under the loaded condition only 180 degrees of the bearing surface will

be in contact in the loading direction.

2. Therefore, a fixed semicircular surface as wide as the ball bearing will be constrained, so that it

can‟t move in either direction & can not rotate.

3. And on the other side of the journal bearing which act as a pivot joint in its original positon, so in

the same semicircular fashion it has been constrained, expect its left free about its roation axis.

Since the crankshaft is supported on the bearings hence the boundary conditions are applied at those

regions. Here in this case only the bending stresses are considered.

7.7 Defining the Loading conditions: Basically there are two different loads act on the crankshaft.

1. Bending Force applied to the crankshaft due to gas combustion in the cylinder.

2. Torsional Force applied to the crankshaft due to the inertia of rotating components

Idealization made for the loading condition: It is accepted that the crankshaft is a shaft with at least two backings.

Every crankshaft must be planned or checked at any rate for two wrench positions, one when the

bowing minute is greatest, and the other when the turning minute is a most extreme.




The extra minutes because of the flywheel weight, belt strain and different powers must be

considered.

It is accepted that the impact of the bowing powers does not expand two course between which a

power is connected.

The crankshaft must be sufficient rigid, when it is subjected vibrate violently under the periodic

forces.[1] [2]

For the given assignment crankshaft is analyzed for the crank on dead center, where surface load of

about 100N is applied in the crank pin region as a bearing load in an angle of120° for the finite

element model as shown in the figure5.

Figure 5: Loading & Boundary condition details

The stresses induced in the crankshafts are bending and also shear stresses due to torsional moment

of the shaft.

7.8 Analytical calculation of the crankshaft when crank at dead centre: Crank at dead centre: when the crank is on dead centre the maximum bending moment will act in the

crankshaft. The thrust in the connecting rod will be equal to piston gas load (F), W is the weight of

the flywheel acting download and T1 and T2 is belt pull acting horizontally. There will be horizontal

reactions RH1(F) at left bearing and RH2(F) at right bearing. The dimensions for the given mono-

crankshaft is a as shown in the figure6.




Figure 6.: Dimensions of the crankshaft

7.9 To find the reactions at RH1(F) and RH1(F)

In this position there will be no twisting moment, and various parts will be designed for bending

only.




7.10 Calculation for stress: 1. The crank web is designed for eccentric loading. There will be two stresses on it, one is the

compressive stress and other is the bending stress due to the load F.[7]

2. From the dimensions of the given crankshaft,

3. Width of the web, W= 22.86 mm

4. The thickness of the web, h= 4.398 mm

7.11 Direct Stress acting on the crankshaft σd

7.12 Solver Bending stress, σb

VIII. PROBLEM SOLVING

In this chapter geometric modeling, design assumption, material properties details are discussed

below:

8.1 Design requirement of the Mono Crankshaft The Mono crankshaft used is the center crankshaft. The bearing pressures are very important in the

design requirement of crankshafts. The maximum permissible bearing pressure depends upon the




maximum gas pressure, journal velocity, amount and method of lubrication and change of direction

of bearing pressure. The following two types of stresses are induced in the crankshaft.

1. Bending Stress

2. Shear stress due to the torsional moment on the shaft.

IX. RESULT AND DISCUSSION

A) Resultant Contact Force Stress analysis is carried out based on the Static or steady state condition, where the solution is

independent of time. Inertial forces are either ignored or neglected and so there is no requirement to

calculate actual time derivatives. Before analysis the basic assumptions are made as shown below:

1. All deformations and strains are small.

2. Structural deformations are proportional to the loads applied.

3. All materials behave in a linear elastic fashion. Hence, the material deforms along the straight

line portion of the stress-strain curve. Highly localized stress concentrations are usually permitted

as long as gross yielding does not take place.

4. Loads are all static. This means that the loads are applied to the structure in a slow or steady

fashion and in a way that makes them time independent

5. No boundary condition varies with time or application of load.

To perform a stress analysis of a crankshaft ANSYS 10 software is used, meshed model of Mono-

Crankshaft with steel as a material property as shown in the table3. is imported from the

HYPERMESH 7 software.

Sl No Component Material Young’s

Modulus

Poisson’s

Ratio

Yield

strength

1 Crankshaft Steel 2.1e5 MPa 0.3 250 MPa

Table 3: Material properties of Forged Steel for a crankshaft

1. Solver used to analyze this problem is Ansys10, for a given loading & boundary conditions to

verify the results. The results generated are as shown below:

A) Displacement Vector Sum:

Figure 7: Nodal Solution of the overall displacement plot




The graphical representation of the above figure7, shows the displacement variation on several

location of the crankshaft. The maximum displacement observed due to surface load is 0.335e-3

B) Von-mises stress plot:

Figure 8 : Nodal Solution of the Von-misess stress plot of a crankshaft

From the element solution of von Mises stresses plot we can observe the stress in the several location

of the crankshaft, Based on the graphical representation of the stresses as shown in the above figure9

, the critical locations are identified & discussed below. The Maximum stress observed is 8.707 Mpa.

Figure 9: Zoomed view of the Von-mises stress plot at the sharp corner's




Figure 10: Reaction solution for the Stress Analysis of a crankshaft

Above figure.10 shows overall reaction force obtained for a given loading condition. Therefore Total

Reaction force should be equal to the total force applied. From the above figure we can observe that

the total reaction force obtained is 100 N and at the each bearing constrained location 50.054N &

49.946N is observed.

C) Comparison between FEA & Analytical results The results from the FEA & Analytical shows the magnitude of the stress are equal for the given

crankshaft model. But FEA results shows different values in the location of the sharp corners b/w the

web & crank pin & at near by bearing region. Because of its eccentric cylinders, geometry which

results in changes in the “K” Value around the sharp corners.

Table 4: Comparison between FEA & Analytical results

9.1 Suggestion for the design improvement: According to the FE Analysis results due to the high stress concentrations at the sharp corners, the

geometric model require design changes mainly in the sharp corner‟s by providing surface fillet of

radius 1.5mm as shown in the figure11 below




Figure 11: Modified Geometric model of an crankshaft

9.2 Modal Analysis of Mono Crankshaft It is the technique used to determine a structure‟s vibration characteristics of a structure or machine

components, mainly:

Modal investigation is utilized to locate the regular frequencies a structure

The frequencies are ascertained in expanding request of recurrence greatness. Clients can

characterize number of frequencies wanted or a scope of recurrence extents.

Two things are critical - mode shape and recurrence. The real estimations of removal are not

physically significant, just the state of the twisting is imperative.

The data modular examination gives is to a great degree profitable - it can settle on outline

choices without encourage vibration investigation required.[4]

The crankshaft experiences a complex loading due to the motion of the connecting rod, which

transforms two sources of loading to the crankshaft. Inertia of rotating components, with the increase

of engine speed. And the dynamic loading because of the magnitude & direction of the load changes

during a cycle. It is essential that to do free free modal analysis of a crankshaft because to know the

behavior, stiffness & mode shape of the component for a given material. Therefore a free free modal

analysis is carried out for the given mono crankshaft FE Model for the two material properties as

shown in the table below:

Table 5: Material properties detail for the Free Free Modal Analysis of a crankshaft

X. CONCLUSION

1. When compared with the volumetric FE models, the structured model has a higher performance

during the dynamic simulation. Because it requires a lower effort and lower hardware

requirements during the stress analysis. The strength analysis is performed only on finely meshed

detailed sub-models of the highest loaded parts of the crankshaft.

2. The detection of the highest loaded parts is support by calculated fillet stresses and safety factors

based on the force applied.

3. Hence it is recommend that before going to analyzed through the FE model, its better to analyze

on the simple Mathematical model. So that it reduces the computational time and resources. Even

designer can understand the behavior of structure and can realize the error‟s & can modify in the

design faster.




REFERENCES I. R. G. Desavale and A. M. Patil on ‘’Theoretical and Experimental Analysis of Torsional and Bending Effect on

Four Cylinders Engine Crankshafts by Using Finite Element Approach’’ in International Journal of Engineering

Research (ISSN : 2319-6890) Volume No.2, Issue No. 6, pp : 379-385

II. Farzin H. Montazersadgh and and Ali Fatemi on ‘’Dynamic Load and Stress Analysis of a Crankshaft’’ in SAE

International 2007.

III. K. Thriveni and Dr.B.JayaChandraiah2 on ‘’Modeling and Analysis of the Crankshaft Using Ansys Software’’

in International Journal of Computational Engineering Research||Vol, 03||Issue, 5||

IV. Ms.Shweta Ambadas Naik on ‘’ Failure Analysis of Crankshaft by Finite Element Method-A Review’’ in

International Journal of Engineering Trends and Technology (IJETT) – Volume 19 Number 5 – Jan 2015

V. Lohitesh Jaga Kumar, Praveen D.N, R.Thara, Irfan G on “ Experimental & Finete Element Analysis Of Sisal

Fiber Reinforced Composites” In International Journal Of Recent Trends In Engineering And Research ||Vol,2||

Issue,7|| July-2016

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STUDY OF THE STATIC STRUCTURAL ANALYSIS OF THE MONO ... · effectiveness of a Mono crankshaft in meeting the intent of the design. A finite element model was created as the first