Design and Analysis of a Shock Absorber by Varying Spring ...

International Journal of Engineering Science and Computing, June 2019 22836 http://ijesc.org/

ISSN XXXX XXXX © 2019 IJESC

Design and Analysis of a Shock Absorber by Varying Spring

Materials – Analysis using Fea Technique T. kalyani

1, J. Srilatha

2, M. Shobha

3 Associate Professor

1, Assistant Professor

2, 3

Department of Mechanical

Raghu Engineering College, Visakhapatnam, Andhra Pradesh, India

Abstract:

Shock absorber suspension system is an important part of automobile motorcycle suspensions designed to smooth out or damp shock

impulse, and dissipate energy. Automobile suspension plays a very important role in stability of the vehicle and passenger comfort

during travelling. In a vehicle, it reduces the effect of travelling over rough ground, leading to improved quality, and increase in

comfort due to substantially reduced amplitude of disturbances. Materials used in suspension system are a key factor in designing the

components and testing the feasibility for operation. Conventionally used springs made of steel material, faced a lot of hindrance in

increasing the engine efficiency and weight of the two wheeler automobile spring suspension. In this paper, a shock absorber for

motor vehicle used in automobile applications is designed by using 3D parametric software CATIA V5 and optimized wire diameter

of 8mm for the suspension spring. Analysis is carried out for a weight of one bike and one person is opted by combining the steel

material, structural steel and metal alloys ASTM 228, Chrome Vanadium and In conel X 750 steel. The prime motto of this work is to

design and analyze the optimum material strength and to reduce the stress and deflection of helical spring by using finite element

analysis performing static structural, modal and transient analysis to validate the strength of design. Comparison of various materials

has been done to check the best suited material by total deformation and equivalent stress. The suspension 3D model is created in

CATIA V5R20 and the model is structurally analyzed using ANSYS 16.0. The results obtained from the design analysis proved that

chrome vanadium alloy material is best suited for spring, and the design falls under safe limits.

Key Words: Helical Spring, CATIA V5, Ansys 16.0, ASTM 228, Chrome Vanadium and Inconel X 750 steel.

I. INTRODUCTION

Spring is defined as an elastic body, whose function is to distort

when loaded and to recover its original shape when the load is

removed. Springs are usually made out of spring steel. Some

non-ferrous metals are also used including phosphor bronze and

titanium for parts requiring corrosion resistance and beryllium

copper for springs carrying electrical current (because of its low

electrical resistance).Helical springs are simple forms of springs,

commonly used for the suspension system in wheeled vehicles.

The major stresses produced in helical springs are shear stresses

due to twisting vehicle suspension system are made out of

springs that have basic role in power transfer, vehicle motion

and driving. The automobile industry tends to improve the

comfort of user and reach appropriate balance of comfort riding

qualities and economy. The load carrying ability of the spring

depends on the diameter of the wire, outer diameter, pitch,

strength of the material and few more design parameters.

1.1. Vehicle Suspension:

In a vehicle, it reduces the effect of travelling over rough

ground, leading to improved ride quality, and increase in

comfort due to substantially reduced amplitude of disturbances.

Shock absorbers allow the use of soft (lower rate) springs while

controlling the rate of suspension movement in response to

bumps. Spring-based shock absorbers commonly use coil springs

or leaf springs, though torsion bars can be used in tensional

shocks as well. Vehicles typically employ springs and torsion

bars as well as hydraulic shock absorbers. There are a number of

different methods of converting an impact /collision into

relatively smooth cushioned contact; they are Metal Spring,

Rubber Buffer, Hydraulic Dashpot, Collapsing safety Shock

Absorbers, Pneumatic Cylinders, and Self compensating

Hydraulic. In this paper, a shock absorber for motor vehicle used

in automobile applications is designed by using 3D parametric

software CATIA V5 and optimized wire diameter of 8mm is

taken for the shock absorber spring. To validate the strength of

design, structural analysis, modal analysis and transient analysis

done on the shock absorber. Analysis is carried out by varying

spring materials.

1.2. Applications

Shock absorbers are an important part of automobile and

motorcycle suspensions, aircraft landing gear, and supports for

many industrial machines. Large shock absorbers have also been

used in structural engineering to reduce the susceptibility of

structures to earthquake damage and resonance. A transverse

mounted shock absorber, called a yaw damper, helps keep

railcars from swaying excessively from side to side and are

important in passenger railroads, commuter rail and rapid transit

systems because they prevent railcars from damaging station

platforms. The success of passive damping technologies in

suppressing vibration amplitudes could be ascertained with the

fact that it has a market size of around 315 billion rupees.

1.3. Objective of the Paper:

The main objective of the work is design and analysis of

automobile shock absorber using software's CATIA for design

Research Article Volume 9 Issue No. 6

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and ANSYS 16.0 for analysis purpose To validate the strength of



spring materials. Static Structural analysis is performed to obtain

the deformation and equivalent stress values. Modal analysis is

performed to obtain frequency and respective deformation

values. Transient analysis is performed to observe varying

deformation values with respect to time.

2. DESIGN PARAMETERS OF SHOCK ABSORBER

SPRING

Mean diameter of a coil (D) = 48 mm Diameter of wire (d) = 8 mm Number of turns (n) = 16 wire Free length (L) = 256 mm Pitch (p) = 16 mm Spring index (c = D/d) = 6 Outer diamerter of spring coil (Do = D + d) = 56 mm Shear modulous for structural steel (G) = 75000 Mpa Weight of the bike = 150 Kgs Let, weight of person = 80 Kgs Total Weight (Bike + 1 Person) = 230 kgs Weight acting on the rare suspension= 65 % of Total Weight = 150 Kgs Considering dynamic loads it will be double, W = 300 Kgs = 2940 N Weight acting on one shock absorber = 1470 N

Figure.1.1. Design of Helical spring

2.1 .Design Calculations for helical spring: Spring Index (C) = D d⁄ = 48 8⁄ = 6 Stress factor (K) = (4C − 1) (4C − 4)⁄

(4 × 6 − 1) 4 × 6 − 4)⁄ = 23 20⁄ = 1.15

Maximum Shear Stress (τ) = (8 × F × D × K) (π × d3)⁄

= (8 × 1470 × 48 × 1.15) 3.14 × 83⁄ = 403.577 Mpa Maximum Deflection (γ max) = (8 × F × D3 × n) (d4 × G)⁄

= (8 × 1470 × 483 × 16) 75000 × 84⁄ = 67 mm

3. INTRODUCTION TO CATIA

CATIA is a multi platform 3D software suite developed by

Dassault Systems, encompassing CAD, CAM as well as CAE.

CATIA is a solid modeling tool that unites the 3D parametric

features with 2D tools and also addresses every design-to-

manufacturing process. The bi-directionally associative property

of CATIA ensures that the modifications made in the model are

reflected in the drawing views and vice-versa.

Engineering Design: CATIA offers a range of tools to enable

the generation of a complete digital representation of the product

being designed. A number of concept design tools that provide

up-front Industrial Design concepts can then be used in the

downstream process of engineering the product. These range

from conceptual Industrial design sketches, reverse engineering

with point cloud data and comprehensive freeform surface tools.

Different modules in CATIA:-

Sketcher

Part design

Assembly

Sheet metal

Figure. 3.1. 3D shock absorber of a Helical Spring

4. INTRODUCTION TO FEA:

Finite Element Analysis (FEA) was first developed in 1943 by

R. Courant, who utilized the Ritz method of numerical analysis

and minimization of variation calculus to obtain approximate

solutions to vibration systems. Shortly thereafter, a paper

published in 1956 by M. J. Turner, R. W. Clough, H. C. Martin,

and L. J. Topp established a broader definition of numerical

analysis. The paper centered on the "stiffness and deflection of

complex structures". By the early 70's, FEA was limited to

expensive mainframe computers generally owned by the

aeronautics, automotive, defense, and nuclear industries. FEA

consists of a computer model of a material or design that is

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stressed and analyzed for specific results. Modifying an existing

product or structure is utilized to qualify the product or structure

for a new service condition. In case of structural failure, FEA

may be used to help determine the design modifications to meet

the new condition. There are generally two types of analysis that

are used in industry: 2-D modeling, and 3-D modeling. While 2-

D modeling conserves simplicity and allows the analysis to be

run on a relatively normal computer, it tends to yield less

accurate results. 3-D modeling, however, produces more

accurate results while sacrificing the ability to run on all but the

fastest computers effectively. Within each of these modeling

schemes, the programmer can insert numerous algorithms

(functions) which may make the system behave linearly or non-

linearly. A wide range of objective functions (variables within

the system) are available for minimization or maximization:

Mass, volume, temperature

Strain energy, stress strain

Force, displacement, velocity, acceleration

Synthetic (User defined)

There are multiple loading conditions which may be applied to a

system. Some examples are shown:

Point, pressure, thermal, gravity, and centrifugal static

loads

Thermal loads from solution of heat transfer analysis

Enforced displacements

Heat flux and convection

Point, pressure and gravity dynamic loads

5. INTRODUCTION TO ANSYS:

ANSYS is general-purpose finite element analysis (FEA)

software package. Finite Element Analysis is a numerical

method of deconstructing a complex system into very small

pieces (of user-designated size) called elements. The software

Implements equations that govern the behavior of these elements

and solves them all; creating a comprehensive explanation of

how the system acts as a whole. These results then can be

presented in tabulated or graphical forms. ANSYS is the

standard FEA teaching tool within the Mechanical Engineering

Department at many colleges. ANSYS provides a cost-effective

way to explore the performance of products or processes in a

virtual environment. This type of product development is termed

virtual prototyping.

5.1. Generic Steps to Solving any Problem in ANSYS:

Solving any problem analytically, need to define (1) solution

domain, (2) physical model, (3) boundary conditions and (4)

physical properties.

Generic steps involve to: Build Geometry, Define Material

Properties, Generate Mesh, Apply Loads, and Obtain Solution,

finally present the Results.

5.2. Types of Analysis Carried out on Shock Absorber for

various materials for 1bike + Person weight (230 Kgs):

5.2.1. Static Structural Analysis:

It is used to determine displacements, stresses, etc. under static

loading conditions. ANSYS can compute both linear and

nonlinear static analyses. Nonlinearities can include plasticity,

stress stiffening, large deflection, large strain, hyper elasticity,

contact surfaces, and creep.

4.2.2. Modal Analysis:

A modal analysis is typically used to determine the vibration

characteristics (natural frequencies and mode shapes) of a

structure or a machine component while it is being designed.

4.2.3. Transient Dynamic Analysis: It is used to determine the response of a structure to arbitrarily

time-varying loads. All nonlinearities mentioned under Static

Analysis above are allowed.

Imported model of Shock absorber using Ansys workbench

Figure.5.1. Imported model of Shock absorber using Ansys

workbench

4.3. Analysis of shock absorber using ANSYS

5.3.1. - Case 1. Structural analysis for weight of Bike + 1

Person (230 kg) using,

Structural steel material:

Load 230 kgs

Material: Structural steel

Material Properties:

Young’s Modulus: 2.00E+02 GPa, Yield strength: 2.50E+02

Mpa, Poisson’s Ratio: 0.3, Density: 7850 kg/m3

Figure.5.2. Equivalent Stress

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Figure .5.3. Total Deformation in mm

Figure.5.4. Equivalent Strain

Figure .5.5. Shear Stress


Person (230 kg) using metal alloys - Music wire (ASTM 228):

Load 230 Kgs

Material: Music wire (ASTM 228):



Mpa, Poisson’s Ratio: 0.29, Density: 7800 kg/m3

Figure.5.6. Equivalent Stress

Figure .5.7. Total Deformation in mm


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Figure.5.9. Shear Stress

5.3.3- Case 3. Structural analysis for weight of Bike + 1 Person

(230 kg) using metal alloys - Metal Alloys (Chrome Vanadium):

Load 230 kgs

Material: Chrome Vanadium



Mpa, Poisson’s Ratio: 0.29, Density: 7861.1 kg/m3

Figure .5.10. Equivalent Stress

Figure.5.11. Total Deformation in mm

Figure .5.12. Equivalent Strain



Person (230 kg) using metal alloys - Metal Alloys (Inconel X

750):

Load 230 kgs

Material: Inconel X 750



Mpa, Poisson’s Ratio: 0.29, Density: 8248.6 kg/m3

Figure .5.14. Equivalent Stress

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Figure. 5.15. Total Deformation in mm



5.4. Modal analysis on shock absorber:

Modal analysis is carried out in order to find out the mode

shapes at different frequencies. It is helpful in finding out the

frequency at which the deformation obtained will be minimum.

In this, difference frequency values with respective deformation

values are obtained.

5.4.1. Modal Analysis at 4.4604 Hz:-

Figure. 5.18. Total deformation at 4.4604Hz


Figure. 5.19: Total deformation at 4.4682 Hz


Figure. 5.20. Total deformation at 18.097 Hz

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5.4.4. Modal Analysis at 18.161 Hz

Figure .5.21. Total deformation at 18.161 Hz


Figure .5.22. Total deformation at 22.076 Hz


Figure. 5.23: Total deformation at 36.307 Hz

4.4. Transient dynamic analysis Transient structural analysis (also called time-history analysis)

specifically uses the ANSYS Mechanical APDL solver. This

type of analysis is used to determine the dynamic response of a

structure under the action of any general time-dependent loads.

5.5.1. Transient Analysis at 0.2 Seconds

Figure .5.24. Transient Analysis at 0.2 Seconds


Figure .5.25.Transient Analysis at 0.2 Seconds


Figure.5.26. Transient Analysis at 0.2 Seconds

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Figure.5.27. Transient Analysis at 0.2 Seconds


Figure .5.28. Transient Analysis at 1.0 Seconds

6. RESULTS AND DISCUSSIONS:

6.1. Structural Analysis Results:

From the structural analysis seen in section 5.3.1 to 5.3.4 (case 1

to 4 – varying materials) the total deformation, equivalent stress,

equivalent strain and shear stress values obtained from the

ANSYS were shown in the below table:

Table. 6.1. Total deformation, equivalent stress, and

equivalent strain and shear stress values from structural

analysis

Material

name

Total

Deforma

tion

(mm)

Max

Equivale

nt Stress

(Mpa)

Max

Equivale

nt Strain

Max

Shear

Stress

(Mpa)

Structural

steel

60.272 877.91 0.0054 345.05

Music

wire(AST

M 228)

59.76 859.79 0.0047 356.44

Chrome

vanadium

(ASTM

231)

58.906 858.57 0.0052 383.78

Inconel

x750

57.863 859.78 0.0044 363.24

4.5. Modal Analysis Results

From the Modal analysis seen in section 5.4.1 to 5.4.6, modal

analysis at varying frequencies, the total deformation values and

the frequencies obtained were less Max deformation of 28.51

mm at 22.076 Hz frequency. Table representing the obtained

values representing the frequency and deformation values is

given below:

Table .6.2. Modal analysis results

Mode no. Frequency (Hz) Deformation

(max in mm)

1 4.4604 44.454

2 4.4682 44.454

3 18.097 68.467

4 18.161 68.331

5 22.076 28.51

6 36.307 46.371

6.3. Transient Analysis Results:

From the transient analysis seen in section 5.5.1 to 5.5.5,

transient analysis at varying time, the obtained deformation

values were tabulated in the table below: Table representing the

time varying deformation at an interval of 0.2 sec for 1 second

obtained values is shown in the table 6.3 below:

Table 6.3: Transient Analysis Results

Time in seconds Total deformation in

mm

0.2 57.367

0.4 58.011

0.6 57.121

0.8 58.205

1.05 58.078

7. CONCLUSION

In this paper, a shock absorber for motor vehicle used in

automobile applications is designed by using 3D parametric

software CATIA V5 and optimized wire diameter of 8mm is

taken for the shock absorber spring. To validate the strength of



spring materials.

From the above analysis, it is observed that the analyzed

stress values are lesser than their respective stress values from

the theoretical calculations. So design is safe.

By comparing the results for both materials, it is observed

that the stress value is less for metal alloy materials than the

Structural steel.

Modal analysis performed on the shock absorber and

different mode shapes are obtained at different frequencies and

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also frequency value is observed at which less deformation

occurs.

Transient structural analysis performed on the shock absorber

and deformation values varying with time are obtained.

Hence from the design analysis it is concluded that, by using

alloy materials - chrome vanadium for the spring is best suited

when compared with the structural steel and other alloy

materials, also by performing the structural analysis, the results

obtained were in safe limits.

8. REFERENCES

[1]. Machine design by R.S.KURMI

[2]. PSG, 2008.” DESIGN DATA,” kalaikathir achachgam

publishers, COIMBATORE, INDIA

[3]. Automobile Engineering by R.B.Gupta

[4]. Automobile Engineering by G.B.S. Narang.

[5]. Automobile Servicing and Maintenance by K.Ashrif Ali

[6]. Automotive Maintenance and Trouble Shooting by Ernest

Venk,& Edward D. Spicer

[7]. Vijayeshwar BV, Preetham B,M, Bhaskar U (2017), “Static

Analysis of Helical Compression Spring”, International

Advanced Research Journal of Science, Engineering and

Technology, May 2017, Volume 4, Issue 7, pp 94-98.

[8]. N. Sai Kumar, R.Vijay Prakash (2016), “Design and

Analysis of Spring Suspension System”, International Journal of

Professional Engineering Studies, November 2016, Volume 7,

Issue 4, pp 315-321.

[9]. Suraj R. Bhosle, Shubham R. Ugle, Dr. Dhananjay R. Dolas

(2017),“Comparative Analysis of Suspension System Coil

Spring Using FEA”, International Journal of Interdisciplinary

Research (IJIR), 2017, Volume 1, Issue 1, pp 757-761.

[10]. MacArthur, L. Stewart (2014), “A Computational

Approach for Evaluating Helical Compression Springs”,

International Journal of Research In Engineering and

Technology, December 2014, Volume 3, Issue 12, pp 224-229.

[11]. P.R. Jadhav, N.P. Doshi, U.D. Gulhane (2014), “Analysis

of Helical Spring in Dual suspension System Used in

Motorcycle”, International Journal of Advanced Engineering

Research and Studies, October 2014, Volume 2, Issue 10, pp

117-121.

[12]. Settey Thriveni, G. Ranjith Kumar, Dr.G. Harinath Gowd

(2014), “Design, Evaluation & Optimization of A Two- Wheeler

Suspension System”, International Journal of Emerging

Technology and Advanced Engineering, August 2014, Volume

4, Issue 8, pp 370-374.

[13]. Niranjan Singh (2013), “General Review of Mechanical

Springs used in Automobile Suspension System”, International

Journal of Advanced Engineering Research and Studies,

October-December 2013, Volume 3, Issue 1, pp 115-122.

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