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1. INTRODUCTION

1.1 Introduction

A suspension system or shock absorber is a mechanical device designed

to smooth out and dissipate kinetic energy. The shock absorbers function is to absorb

or dissipate energy. In a vehicle, it reduces the effect of traveling over rough ground,

leading to improve ride quality, and increase in comfort due to substantially reduced

amplitude of disturbances.

Basic safety and also traveling ease and comfort to get a cars motorist are usually equally influenced by the particular vehicles suspension method. Safety refers to the vehicles handling and braking capabilities. Shock absorbers are a critical part of a suspension system, connecting the vehicle to its wheels. Basically

shock absorbers tend to be products which lessen a good behavioral instinct skilled

with an automobile, as well as properly absorb the actual kinetic power. Almost all

suspension systems consist of springs and dampers, which tend to limit the

performance of a system due to their physical constraints. Suspension systems,

comprising of springs and dampers are usually designed for passengers safety and do little to improve passenger comfort.

One particular strategy to this can be the application of productive

suspension devices, wherever highway circumstances are generally found

employing detectors, plus the technique in a flash adapts on the placing. A shock

absorber is a device which is designed to smooth out sudden impulse responses, and

dissipate kinetic energy. Any moving object possesses kinetic energy, and if the

object changes direction or is brought to rest, it may dissipate kinetic energy in the

form of destructive forces within the object. The purpose of a shock absorber, within

any moving object, is to dissolve the kinetic energy evenly while eliminating any

decelerating force that may be destructive to the object.

Shock absorbers are an important part of automobile and motorcycle

suspensions, aircraft landing gear, and the supports for many industrial machines.

Large shock absorbers have also been used in structural engineering to reduce the

susceptibility of structures to earthquake damage. A transverse mounted shock

absorber, helps keep railcars from swaying excessively from side to side and are

important in passenger railroads systems because they prevent railcars from

damaging station platforms. In a vehicle, it reduces the effect of traveling over rough

ground, and leading to improved ride quality. Without shock absorbers, the vehicle

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would have a bouncing ride, as energy is stored in the spring and then released to

the vehicle, possibly exceeding the allowed range of suspension movement.

A typical shock absorber may simply comprise of a compression spring

that is capable of absorbing energy. Commonly shock absorbers are known as

dashpots, which is simply a fluid filled cylinder with an aperture through which fluid

could escape under controlled conditions. The dashpot is the building block for

pneumatic and hydraulic shock absorbers. These shock absorbers essentially consist

of a cylinder, filled with air or fluid, with a sliding piston that moves to dissipate or

absorb energy, and in these cases the energy is usually dissipated as heat.

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1.2 Objectives of the Project

Study the causes of bouncing problems of the vehicle. Compare the failure parts performance in terms of its yield strength between

beryllium copper and spring steel.

Springs in parallel combination is used further for a comfortable ride.

1.3 Scope of Study

The scope of study for this project includes:-

Applying structural and modal analysis on the shock absorber.

Applying dynamic analysis on the shock absorber.

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2. LITERATURE SURVEY

2.1 Shock Absorber

The shock absorber is really a mechanized gadget made to lessen

or even moist surprise behavioral instinct, as well as dissolve kinetic power. It's a

kind of dashpot. The shock absorber function is to absorb or dissipate energy. One

design consideration, when designing or choosing a shock absorber, is where that

energy will go. In many dashpots, power is actually transformed into warmth within

the viscous liquid. Within hydraulic cylinders, the actual hydraulic liquid gets hotter,

during atmosphere cylinders, the actual heat is generally worn out towards the

environment. In other types of dashpots, such as electromagnetic types, the

dissipated energy can be stored and used later. In general terms, shock absorbers

help cushion vehicles on uneven roads.

Shock absorbers tend to be an essential a part of car as well as

motorbike suspensions, plane getting equipment, and also the facilities for a lot of

commercial devices. Big shock absorbers are also utilized in structural architectural

to lessen the actual susceptibility associated with buildings in order to earthquake

harm as well as resonance. The transverse installed shock absorber, known as the

yaw damper, helps maintain railcars through swaying too much laterally and

therefore are essential within traveler railroads, commuter train as well as quick

transit techniques simply because they avoid railcars through harmful train station

systems.

Inside a vehicle, shock absorbers slow up the effect associated

with travelling more than rough floor, leading in order to improve trip quality as well

as increase within comfort. While surprise absorbers serve the objective of limiting

extreme suspension motion, their meant sole purpose would be to dampen

springtime oscillations. Shock absorbers make use of valve associated with oil as

well as gasses to soak up excess energy in the springs. Spring prices are chosen

through the manufacturer in line with the weight from the vehicle, packed and

unloaded. Some individuals use shocks to change spring prices but this isn't the

proper use. Together with hysteresis within the tire by itself, they dampen the power

stored within the motion from the unsparing weight down and up. Effective steering

wheel bounce damping may need tuning shocks for an optimal opposition.

Spring-based surprise absorbers generally use coils springs or

even leaf comes, though torsion bars are utilized in torsion shocks too. Ideal comes

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alone, nevertheless, are not really shock absorbers, as come only store and don't

dissipate or even absorb power. Vehicles usually employ each hydraulic surprise

absorbers as well as springs or even torsion pubs. In this particular combination,

"shock absorber" pertains specifically towards the hydraulic piston which absorbs as

well as dissipates vibration.

2.2 Main components of Shock Absorber

Shock absorber has three main components to make it function well.

They are damper, spring and bushing. These all three part are playing an important

role to work together and absorb the impact or bouncing.

2.2.1 Damper

Damper shock absorber or simply damper is device that is designed

for providing absorption of shock and smooth deceleration in linear motion

applications. The dampers can be either mechanical or rely on a fluid. Dampers like

other shock absorber absorb shock by controlling the flow of the fluid from outer to

inner chamber of a cylinder during piston actuation. The damper shock absorbers

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can be adjusted to different road conditions and provides good balance to the

vehicles.

2.2.2 Spring

Spring shock absorber as the name suggests is used to absorb the

jerks or bumps by using coil spring. The spring shock absorber is given stiffer

character by tightening the spring. The center of the spring shock absorber usually

contains rebound dampening unit. As the shock absorber changes the length the flow

fluid inside the shock absorber starts.

Springs length is usually controlled by turning the disc at the

bottom of the spring on the threads. The shorter spring length increases the preload,

making the rear wheel more resistant to upward motion. The dampening is both

controlled and adjusted in the spring shock absorber by controlling the fluid

reservoir. If the dampening is increased the motion of the shock is slowed down.

The spring type of shock absorbers are usually utilized for

protecting the delicate mechanisms, like instruments, from direct impact or loads

that are applied instantaneously. These types of springs are often made of rubber or

similar elastic material.

The springs that are used in different spring based shock absorbers

are coil springs or leaf springs. In tensional shocks, torsion bars can be used. In most

of the vehicles, springs or torsion bars as well as hydraulic shock absorbers are used.

2.2.3 Bushing

A bushing or rubber bushing is a type of vibration isolator. It

provides an interface between two parts, damping the energy transmitted through the

bushing. A common application is in vehicle suspension systems, where a bushing

made of rubber (or, more often, synthetic rubber or polyurethane) separates the faces

of two metal objects while allowing a certain amount of movement. This movement

allows the suspension parts to move freely, for example, when traveling over a large

bump, while minimizing transmission of noise and small vibrations through to the

chassis of the vehicle. A rubber bushing may also be described as a flexible mounting

or anti vibration mounting.

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2.3 Dynamics of shock absorber

2.3.1 Response due to harmonic excitation of support

Consider the mass-spring-dashpot system of Figure 2.3.1. The

spring and dashpot are in parallel with one end of each connected to the mass and

the other end of each connected to a moveable support. Let y (t) denote the known

displacement of the support and let x (t) denote the absolute displacement of the

mass.

FIGURE 2.3.1 (a) FIGURE 2.3.1 (b)

(a) Block is connected through parallel combination of spring and viscous damper to a moveable support.

(b) FBDs at an arbitrary instant. Spring and viscous damper forces include effects of base motion.

Application of Newtons law to the free-body diagrams of Figure yields

.. (1)

.(2)

(3)

As the displacement of the mass relative to the displacement of its support. Above

equation (2) is rewritten using z as the dependent variable

.(4 )

Dividing Equations (2) by (4) by m yields

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.. (5)

.... (6)

If the base displacement is given by a single-frequency harmonic of the form

y (t) =Y sin t

Then Equations (5) and (6) become

..(7)

..(8)

Equation (8) shows that a mass-spring-dashpot system subject to harmonic base

motion is yet another example in which the magnitude of a harmonic excitation is

proportional to the square of its frequency.

(9)

(10)

When Equations (9) and (10) are substituted into Equation (3) the absolute

displacement becomes

. (11)

Using the trigonometric relationship for the sine of the difference of two angles, it

is possible to express Equation (11) in the form

. (12)

. (13)

(14)

. (15)

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X/Y is the amplitude of the absolute displacement of the mass to the amplitude of

displacement of the base.

Multiplying the numerator and denominator by 2 leads to

..(16)

Equation (15) is plotted in Figure The following are noted about

..(17)

GRAPH - 1

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(18)

4. The maximum T(r, ) corresponding to the frequency ratio of Equation (18)

(19)

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3. METHODOLOGY

3.1 Springs in parallel

FIGURE 3.1

When two springs are connected in parallel, both springs will deflect by

same amount and the load is shared between two springs.

It is observed from the figure, when force F1 is acting on spring of stiffness s1, spring

deflects by an amount . When force F2 (greater than F1) is acting on spring on

stiffness s2, spring deflects by same amount . When force F1+F2 is acting on both

springs, equivalent spring deflects by same amount .

So spring in spring or concentric springs has the following advantages:

Since there are two springs, the load carrying capacity is increased and heavy load can be transmitted in a restricted space.

In concentric spring, the operation of the mechanism continues even if one of the springs breaks.

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3.2 Design Calculations of Helical springs for Shock absorbers

Mean diameter of a coil = D=60mm

Diameter of wire d = 8mm

Total no of coils n= 10

Height h = 185mm

Outer diameter of spring coil Do= D +d =68mm

No of active turns n = 8

Weight of bike = 125 Kgs

Let weight of 1 person = 75 Kgs

Weight of 2 persons = 150 Kgs

Weight of bike + persons = 275 Kgs

Rear suspension = 65% of W

65% of 275 = 165 Kgs

Considering dynamic loads it will be double

W = 330 Kgs = 3234 N

For single shock absorber weight = w/2= 1617 N = W

We Know that, compression of spring () = 8Wxc3xn

Gxd

= 8x1617x83x10 = 201.92 mm

41000x8

10 x 8 =80 mm

10x8+201.92+0.15x201.92=312.2 mm

1617/201.92=8

(312.2+80)/10=39.22 mm

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(0.97x8x1617x8)/ (3.14x82) =499.26 Mpa

312.2/60=5.2

Wcr = 8x 0.05 x 312.2 = 124.88 N

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4. INTRODUCTION TO CAD & NX 7.5

4.1. INTRODUCTION TO CAD

4.2. TECHNOLOGY OF CAD

4.3. PRODUCT DEVELOPMENT THROUGH CAD PROCESS

4.4. INTRODUCTION TO NX 7.5

4.5. SOLID GEOMETRIC MODELING

4.1 INTRODUCTION TO CAD

Computer Aided Design (CAD) is a technique in which man and

machine are blended into problem solving team, intimately coupling the best

characteristics of each. The result of this combination works better than either man

or machine would work alone, and by using a multi discipline approach, it offers the

advantages of integrated team work. The advances in Computer Science and

Technology resulted in the emergence of very powerful hardware and software

tool. It offers scope for use in the entire design process resulting in improvement in

the quality of design. The advent of CAD as a field of specialization will help the

engineer to acquire the knowledge and skills needed in the use of these tools in an

efficient and effective way on the design process. Computer Aided Design is an

interactive process, where the exchange of information between the designer and

the computer is made as simple and effective as possible. Computer aided design

encompasses a wide variety of computer based methodologies and tools for a

spectrum of engineering activities planning, analysis, detailing, drafting,

construction, manufacturing, monitoring, management, process control and

maintenance. CAD is more concerned with the use of computer-based tools to

support the entire life cycle of engineering system of design.

The modern manufacturing environment can be characterized by

the paradigm of delivering products of increasing variety, smaller batches and

higher quality in the context of increasing global competition. Industries cannot

survive worldwide competition unless they introduce new products with better

quality, at lower costs and with shorter lead-time. There is intense international

competition and decreased availability of skilled labor. With dramatic changes in

computing power and wider availability of software tools for design and production,

engineers

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are now using Computer Aided Design (CAD), Computer Aided Manufacturing

(CAM) and Computer Aided Engineering (CAE) systems to automate their design

and production processes. These technologies are now used every day for sorts of

different engineering tasks. Below is a brief description of how CAD technology is

being used during the product realization process.

4.1.1 PRODUCT REALIZATION PROCESS:

The product realization process can be roughly divided into two

phases; design and manufacturing. The design process starts with identification of

new customer needs and design variables to be improved, which are identified by

the marketing personnel after getting feedback from the customers. Once the

relevant design information is gathered, design specifications are formulated. A

feasibility study is conducted with relevant design information and detailed design

and analyses are performed. The detailed design includes design conceptualization,

prospective product drawings, sketches and geometric modeling. Analysis includes

stress analysis, interference checking, kinematics analysis, mass property

calculations and tolerance analysis, and design optimization. The quality of the

results obtained from these activities is directly related to the quality of the analysis

and the tools used for conducting the analysis. This project is mainly concentrated

on product design and its analysis only.

4.1.2 BRIEF HISTORY OF CAD

The roots of current CAD/CAM technologies go back to the

beginning of civilization when engineers in ancient Egypt recognized graphics

communication. Orthographic projection practiced today was invented around the

1800s. Therell development of CAD/CAM started in the 1950s. CAD/CAM went through four major phases of development in the last century. The 1950s was known as the era of interactive computer graphics. MITs Servo Mechanisms Laboratory demonstrated the concept of numerical control (NC) on milling

machine. Development in this era was slowed down by the shortcomings of

computers at the time. During the late 1950s the development of Automatically Programmed Tools (APT) began and General Motors explored the potential of

interactive graphics.

The 1960s was the most critical research period for interactive

computer graphics. Ivan Sutherland developed a sketchpad system, which

demonstrated the possibility of creating drawings and altercations of objects

interactively on a cathode ray tube (CRT). The term CAD started to appear with

the word design extending beyond basic drafting concepts. General Motors

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announced their DAC-1 system and Bell Technologies introduced the

GRAPHIC 1 remote display system. During the 1970s, the research efforts of the previous decade in computer graphics had begun to be fruitful, and potential of

interactive computer graphics in improving productivity was realized by industry,

government and academia. The 1970s is characterized as the golden era for computer drafting and the beginning of ad hoc instrumental design applications.

National Computer Graphics Association (NCGA) was formed and Initial Graphics

Exchange Specification (IGES) was initiated. In the 1980s, new theories and algorithms evolved and integration of various elements of design and manufacturing

was developed. The major research and development focus was to expand

CAD/CAM systems beyond three-dimensional geometric designs and provide more

engineering applications. The present day CAD/CAM development focuses on

efficient and fast integration and automation of various elements of design and

manufacturing along with the development of new algorithms. There are many

commercial CAD/CAM packages available for direct usages that are user-friendly

and very proficient.

Below are some of the commercial packages in the present market.

AutoCAD and Mechanical Desktop are some low-end CAD software systems, which are mainly used for 2D modeling and drawing.

NX, Pro-E, CATIA and I-DEAS, DSS SOLID WORKS are high-end modeling and designing software systems that are costlier but more powerful. These software

systems also have computer aided manufacturing and engineering analysis

capabilities.

ANSYS, ABAQUS, NASTRAN, Fluent and CFX are packages mainly used for analysis of structures and fluids. Different software are used for different proposes.

For example, Fluent is used for fluids and ANSYS is used for structures.

Alibre and Collab CAD are some of the latest CAD systems that focus on collaborative design, enabling multiple users of the software to collaborate on

computer-aided design over the Internet.

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4.1.3. DEFINITION OF CAD/CAM/CAE

Following are the definitions of some of the terms used in this tutorial.

4.1.3a.Computer Aided Design CAD

CAD is technology concerned with using computer systems to assist

in the creation, modification, analysis, and optimization of a design. Any

computer program that embodies computer graphics and an application program

facilitating engineering functions in design process can be classified as CAD

software. The most basic role of CAD is to define the geometry of design a mechanical part, a product assembly, an architectural structure, an electronic circuit,

a building layout, etc. The greatest benefits of CAD systems are that they can save

considerable time and reduce errors caused by otherwise having to redefine the

geometry of the design from scratch every time it is needed.

4.1.3b.Computer Aided Manufacturing CAM

CAM technology involves computer systems that plan, manage, and control

the manufacturing operations through computer interface with the plants production resources. One of the most important areas of CAM is numerical control (NC).

This is the technique of using programmed instructions to control a machine tool,

which cuts, mills, grinds, punches or turns raw stock into a finished part. Another

significant CAM function is in the programming of robots. Process planning is also

a target of computer automation.

4.1.3c.Computer Aided Engineering CAE

CAE technology uses a computer system to analyze the functions of a

CAD-created product, allowing designers to simulate and study how the product

will behave so that the design can be refined and optimized. CAE tools are available

for a number of different types of analyses. For example, kinematic analysis

programs can be used to determine motion paths and linkage velocities in

mechanisms. Dynamic analysis programs can be used to determine loads and

displacements in complex assemblies such as automobiles. One of the most popular

methods of analyses is using a Finite Element Method (FEM). This approach can

be used to determine stress, deformation, heat transfer, magnetic field

distribution, fluid flow, and other continuous field problems that are often too

tough to solve with any other approach.

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4.2. Technology of CAD

CAD technology makes use of drawings of parts and assemblies on

computer files which can be further analyzed and optimized. The

functional, ergonomic and aesthetic features of the product can be

evaluated on the computers. This has been made possible through the use

of the design workstations or CAD terminals and graphics and analytic

software, which help the designer to interactively model and analyze

object or component.

CAD can be put to a variety of uses, some of which are listed below.

1. Create conceptual product model/models.

2. Editing or refining the model to improve aesthetic, ergonomics and

performance,

3. Display the product in several colors to select color combination

most appealing to customers,

4. Rotate and views the object from various sided and direction.

5. Create and display all inner details of the assembly.

6. Check for interference or clearance between mating parts in static

and /or dynamic situations.

7. Analyze stress, static deflection and dynamic behavior for different

mechanical and thermal loading configurations and carry out quickly any

necessary design modifications to rectify deficiencies in design.

8. Study the product from various aspects such as material

requirements, costs, value engineering manufacturing processes,

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standardization, simplification, weight reduction, service life, lubricants,

servicing and maintenance aspects etc.

9. Prepare detailed component drawings giving full details of

dimensions, tolerances, surface finish requirements, functional

specification etc.

10. Prepare assembly drawing depicting the orientation of components,

11. Assembly procedures and requirements and incorporation, as

required, such

12. Prepare exploded view of the assemblies. These views could be so

oriented as to provide better visibility and improved comprehension of the

design. Plot to print the picture/drawing stored in a computer file or the

computer screen on different media.

13. Store the database of the object. Part of the drawing in a magnetic

disc or tape for the retrieval at the later date for the use in some other

design.

4.2.1. Modification of existing design

The above description reveals that CAD technologies give the

design engineer a powerful tool for graphical tasks .Modern CAD

systems are based on interactive computer graphics communicates data

and commands to the computer through the several input devices, to create

an image or model on the computer screen by entering command to call

and active the required software subroutines stored in the computer.

In a 2-dimensional drafting system the images are constructed out of basic

geometric elements or entities like points, lines, arcs, circles etc. These

images can then be modified. Rotated, scaled or transformed in several

ways depending upon the designers requirement.

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4.3. PRODUCT DEVELOPMENT THROUGH CAD PROCESS:

The product begins with a need that is identified based on

costumer and markets demands. The product goes through two main processes from the idea conceptualization to the finished product the

design process and the manufacturing process. Product development

through CAD product. Synthesis and analysis are the main sub processes

that constitute the deign process. Synthesis is crucial to design an analysis.

The philosophy, functionality and uniqueness of the product are all

determined during the synthesis. The major financial commitment to turn

the conceived product idea into reality is also made. Most of the

information generated during the synthesis sod process is qualitative

and consequently is hard to captured in a computer system expert and

knowledge based systems have made a great deal of progress in this regard and the interested conceptual design of the prospective product.

Typically, this design takes the form of a sketch or surrounding constrains.

It is also employed during brainstorming discussions among various

design terms and the presentation purpose.

4.4. Introduction to NX 7.5

NX is one of the worlds most advanced and tightly integrated CAD/CAM/CAE product development solutions. Spanning

the entire range of product development, NX delivers immense value to

enterprises of all sizes. It simplifies complex product designs, thus

speeding up the process of introducing products to the market.

The NX software integrates knowledge-based principles,

industrial design, geometric modeling, advanced analysis, graphic

simulation, and concurrent engineering. The software has powerful

hybrid modeling capabilities by integrating constraint-based feature

modeling and explicit geometric modeling. In addition to modeling

standard geometry parts, it allows the user to design complex free-form

shapes such as airfoils and manifolds. It also merges solid and surface

modeling techniques into one powerful tool set.

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4.5. SOLID GEOMETRIC MODELING:

A solid model of an object is a completed representation of the

object. This model is capable of complex geometry data representation

that is the art completely defined ,solid modeling techniques based on

information ally complete, valid and unambiguous of object solid

modelers store more information (geometry and topology) than wire

frame modelers of surface (geometry only). Both wire frame and surface

modelers are incapable of handling special address ability as well as

verifying that the model is well framed or not. Solid models can be quickly

created without having to define individual locations as with wire

frames. Solid modeling produces accurate designs, provides complete

three-dimensional improves the quality of the design, improves and

has potential for functional automation and integration.

The first step in working in NX is to log on to a workstation and

start an NX session. After you start NX, you see the No Part interface.

You can change defaults and preferences, open an existing part file, or

create a new part file.

FIG4.5

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4.5.1. MODELLING OF SHOCK ABSORBER

1. Outer spring

FIGURE 4.5.1a

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2. Inner spring

FIGURE 4.5.1b

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3. Solid model of outer spring

FIGURE 4.5.1.c

4. Solid model of Inner spring

FIGURE 4.5.1d

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5. Cylinder

FIGURE 4.5.1e

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6. Solid model of cylinder

FIGURE 4.5.1f

7. Hat

FIGURE 4.5.1 g

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8. Rings and Rod

FIGURE 4.5.1 h

FIGURE 4.5.1 i

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FIGURE 4.5.1 J

9. Sequence of assembly

FIGURE 4.5.1K

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FIGURE 4.5.1 L

FIGURE 4.5.1 m

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10. Final model of shock absorber

FIGURE 4.5.1 n

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5. 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 variational

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.

Since the rapid decline in the cost of computers and the phenomenal increase in

computing power, FEA has been developed to an incredible precision. Present day

supercomputers are now able to produce accurate results for all kinds of parameters.

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

and analyzed for specific results. It is used in new product design, and existing

product refinement. A company is able to verify a proposed design will be able to

perform to the client's specifications prior to manufacturing or construction.

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. Linear systems are far

less complex and generally do not take into account plastic deformation. Nonlinear

systems do account for plastic deformation, and many also are capable of testing a

material all the way to fracture.

FEA uses a complex system of points called nodes which make a grid called

a mesh. This mesh is programmed to contain the material and structural properties

which define how the structure will react to certain loading conditions. Nodes are

assigned at a certain density throughout the material depending on the anticipated

stress levels of a particular area. Regions which will receive large amounts of stress

usually have a higher node density than those which experience little or no stress.

Points of interest may consist of: fracture point of previously tested material, fillets,

corners, complex detail, and high stress areas. The mesh acts like a spider web in

that from each node, there extends a mesh element to each of the adjacent nodes.

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This web of vectors is what carries the material properties to the object, creating

many elements. 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

Each FEA program may come with an element library, or one is constructed over

time. Some sample elements are:

Rod elements Beam elements Plate/Shell/Composite elements Shear panel Solid elements Spring elements Mass elements Rigid elements Viscous damping elements

Many FEA programs also are equipped with the capability to use multiple materials

within the structure such as:

Isotropic, identical throughout Orthotropic, identical at 90 degrees General anisotropic, different throughout

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5.1. Types of Engineering Analysis:

Structural analysis consists of linear and non-linear models. Linear

models use simple parameters and assume that the material is not plastically

deformed. Non-linear models consist of stressing the material past its elastic

capabilities. The stresses in the material then vary with the amount of deformation

as in.

Vibrational analysis is used to test a material against random vibrations,

shock, and impact. Each of these incidences may act on the natural vibrational

frequency of the material which, in turn, may cause resonance and subsequent

failure.

Fatigue analysis helps designers to predict the life of a material or

structure by showing the effects of cyclic loading on the specimen. Such analysis

can show the areas where crack propagation is most likely to occur. Failure due to

fatigue may also show the damage tolerance of the material.

Heat Transfer analysis models the conductivity or thermal fluid

dynamics of the material or structure. This may consist of a steady-state or transient

transfer. Steady-state transfer refers to constant thermo properties in the material that

yield linear heat diffusion.

5.2. Results of Finite Element Analysis

FEA has become a solution to the task of predicting failure due to unknown

stresses by showing problem areas in a material and allowing designers to see all of

the theoretical stresses within. This method of product design and testing is far

superior to the manufacturing costs which would accrue if each sample was actually

built and tested. In practice, a finite element analysis usually consists of three

principal steps:

1. Preprocessing: The user constructs a model of the part to be analyzed in which

the geometry is divided into a number of discrete sub regions, or elements,"

connected at discrete points called nodes." Certain of these nodes will have fixed

displacements, and others will have prescribed loads. These models can be

extremely time consuming to prepare, and commercial codes vie with one another

to have the most user-friendly graphical preprocessor" to assist in this rather tedious chore. Some of these preprocessors can overlay a mesh on a preexisting CAD file,

so that finite element analysis can be done conveniently as part of the computerized

drafting-and-design process.

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2. Analysis: The dataset prepared by the preprocessor is used as input to the finite

element code itself, which constructs and solves a system of linear or nonlinear

algebraic equations

Kijuj = fi

Where u and f are the displacements and externally applied forces at the nodal points.

The formation of the K matrix is dependent on the type of problem being attacked,

and this module will outline the approach for truss and linear elastic stress analyses.

Commercial codes may have very large element libraries, with elements appropriate

to a wide range of problem types. One of FEA's principal advantages is that many

problem types can be addressed with the same code, merely by specifying the

appropriate element types from the library.

3. Post processing: In the earlier days of finite element analysis, the user would

pore through reams of numbers generated by the code, listing displacements and

stresses at discrete positions within the model. It is easy to miss important trends and

hot spots this way, and modern codes use graphical displays to assist in visualizing

the results. A typical postprocessor display overlays colored contours representing

stress levels on the model, showing a full field picture similar to that of photo elastic

or moir experimental results.

5.3. INTRODUCTION TO ANSYS WORKBENCH

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. This type of

analysis is typically used for the design and optimization of a system far too complex

to analyze by hand. Systems that may fit into this category are too complex due to

their geometry, scale, or governing equations.

ANSYS is the standard FEA teaching tool within the Mechanical

Engineering Department at many colleges. ANSYS is also used in Civil and

Electrical Engineering, as well as the Physics and Chemistry departments.

ANSYS provides a cost-effective way to explore the performance of

products or processes in a virtual environment. This type of product development is

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termed virtual prototyping. With virtual prototyping techniques, users can iterate

various scenarios to optimize the product long before the manufacturing is started.

This enables a reduction in the level of risk, and in the cost of ineffective designs.

The multifaceted nature of ANSYS also provides a means to ensure that users are

able to see the effect of a design on the whole behavior of the product, be it

electromagnetic, thermal, mechanical etc.

An overview of ANSYS WORK BENCH

FIGURE 5.3

5.4. Generic Steps to Solving any Problem in ANSYS:

Like solving any problem analytically, you need to define (1) your solution

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

properties. You then solve the problem and present the results. In numerical

methods, the main difference is an extra step called mesh generation. This is the step

that divides the complex model into small elements that become solvable in an

otherwise too complex situation. Below describes the processes in terminology

slightly more attune to the software.

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Build Geometry

Construct a two or three dimensional representation of the object to be

modeled and tested using the work plane coordinate system within ANSYS.

Define Material Properties

Now that the part exists, define a library of the necessary materials that

compose the object (or project) being modeled. This includes thermal and

mechanical properties.

Generate Mesh

At this point ANSYS understands the makeup of the part. Now define

how the modeled system should be broken down into finite pieces.

Apply Loads

Once the system is fully designed, the last task is to burden the system

with constraints, such as physical loadings or boundary conditions.

Obtain Solution

This is actually a step, because ANSYS needs to understand within what

state (steady state, transient etc.) the problem must be solved.

Present the Results

After the solution has been obtained, there are many ways to present

ANSYS results, choose from many options such as tables, graphs, and contour plots.

5.5. Specific Capabilities of ANSYS:

5.5.1. Structural

Structural analysis is probably the most common application of the finite

element method as it implies bridges and buildings, naval, aeronautical, and

mechanical structures such as ship hulls, aircraft bodies, and machine housings, as

well as mechanical components such as pistons, machine parts, and tools.

Static Analysis - Used to determine displacements, stresses, etc. under static

loading conditions. ANSYS can compute both linear and nonlinear static analyses.

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Nonlinearities can include plasticity, stress stiffening, large deflection, large strain,

hyper elasticity, contact surfaces, and creep.

Transient Dynamic Analysis - Used to determine the response of a structure

to arbitrarily time-varying loads. All nonlinearities mentioned under Static Analysis

above are allowed.

Buckling Analysis - Used to calculate the buckling loads and determine the

buckling mode shape. Both linear (eigenvalue) buckling and nonlinear buckling

analyses are possible.

In addition to the above analysis types, several special-purpose features are

available such as

Fracture mechanics, Composite material analysis Fatigue, and Both p-Method and Beam analyses.

5.5.2. Thermal

ANSYS is capable of both steady state and transient analysis of any solid

with thermal boundary conditions.

Steady-state thermal analyses calculate the effects of steady thermal loads

on a system or component. Users often perform a steady-state analysis before doing

a transient thermal analysis, to help establish initial conditions. A steady-state

analysis also can be the last step of a transient thermal analysis; performed after all

transient effects have diminished. ANSYS can be used to determine temperatures,

thermal gradients, heat flow rates, and heat fluxes in an object that are caused by

thermal loads that do not vary over time. Such loads include the following:

Convection Radiation Heat flow rates Heat fluxes (heat flow per unit area) Heat generation rates (heat flow per unit volume) Constant temperature boundaries

A steady-state thermal analysis may be either linear, with constant material

properties; or nonlinear, with material properties that depend on temperature. The

thermal properties of most material vary with temperature. This temperature

dependency being appreciable, the analysis becomes nonlinear. Radiation boundary

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conditions also make the analysis nonlinear. Transient calculations are time

dependent and ANSYS can both solve distributions as well as create video for time

incremental displays of models.

5.5.3. Acoustics / Vibration

ANSYS is capable of modeling and analyzing vibrating systems in order to

that vibrate in order to analyze Acoustics is the study of the generation, propagation,

absorption, and reflection of pressure waves in a fluid medium. Applications for

acoustics include the following:

Sonar - the acoustic counterpart of radar

Design of concert halls, where an even distribution of sound pressure is desired

Noise minimization in machine shops

Noise cancellation in automobiles

Underwater acoustics

Design of speakers, speaker housings, acoustic filters, mufflers, and many other similar devices.

Geophysical exploration

Within ANSYS, an acoustic analysis usually involves modeling a fluid

medium and the surrounding structure. Characteristics in question include pressure

distribution in the fluid at different frequencies, pressure gradient, and particle

velocity, the sound pressure level, as well as, scattering, diffraction, transmission,

radiation, attenuation, and dispersion of acoustic waves. A coupled acoustic analysis

takes the fluid-structure interaction into account. An uncoupled acoustic analysis

models only the fluid and ignores any fluid-structure interaction.

The ANSYS program assumes that the fluid is compressible, but allows only

relatively small pressure changes with respect to the mean pressure. Also, the fluid

is assumed to be non-flowing and in viscid (that is, viscosity causes no dissipative

effects). Uniform mean density and mean pressure are assumed, with the pressure

solution being the deviation from the mean pressure, not the absolute pressure.

5.5.4. Coupled Fields

A coupled-field analysis is an analysis that takes into account the interaction

(coupling) between two or more disciplines (fields) of engineering. A piezoelectric

analysis, for example, handles the interaction between the structural and electric

fields: it solves for the voltage distribution due to applied displacements, or vice

versa. Other examples of coupled-field analysis are thermal-stress analysis, thermal-

electric analysis, and fluid-structure analysis.

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Some of the applications in which coupled-field analysis may be required are

pressure vessels (thermal-stress analysis), fluid flow constrictions (fluid-structure

analysis), induction heating (magnetic-thermal analysis), ultrasonic transducers

(piezoelectric analysis), magnetic forming (magneto-structural analysis), and micro-

electro mechanical systems (MEMS).

5.5.5. 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. It can also serve as a starting point for another, more detailed,

dynamic analysis, such as a harmonic response or full transient dynamic analysis.

Modal analyses, while being one of the most basic dynamic analysis types available

in ANSYS, can also be more computationally time consuming than a typical static

analysis. A reduced solver, utilizing automatically or manually selected master

degrees of freedom is used to drastically reduce the problem size and solution time.

5.5.6 Harmonic Analysis

Used extensively by companies who produce rotating machinery, ANSYS

Harmonic analysis is used to predict the sustained dynamic behavior of structures to

consistent cyclic loading. Examples of rotating machines which produced or are

subjected to harmonic loading are:

Turbines o Gas Turbines for Aircraft and Power Generation o Steam Turbines o Wind Turbine o Water Turbines o Turbo pumps

Internal Combustion engines

Electric motors and generators

Gas and fluid pumps

Disc drives

A harmonic analysis can be used to verify whether or not a machine

design will successfully overcome resonance, fatigue, and other harmful effects of

forced vibrations.

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5.6. Results:

5.6.1. Structural Analysis for bike weight (165 kgs) using Spring Steel as

Spring material

FOR 165 kg load

Material used: structural steel

E: 210000N/mm^2

Poissons Ratio (PRXY): 0.29

Density: 0.000007850kg/mm3

imported model from NX 7.5

Figure 5.6.1

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5.6.2. Meshed Model

FIGURE 5.6.2

5.6.3. Solution step

FIGURE 5.6.3

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5.6.4. Modal analysis

FIGURE 5.6.4 a

FIGURE 5.6.4 b

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FIGURE 5.6.4.c

FIGURE 5.6.4 d

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5.7. Structural Analysis for bike weight (165kgs) using Beryllium

Copper as spring material

Load=165 kg

Material used: beryllium copper

E : 280000N/mm2

Poissons Ratio (PRXY) : 0.285

Density :0.000001850kg/mm3

FIGURE 5.7

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5.7.1. Modal Analysis for beryllium copper spring

FIGURE 5.7.1 a

FIGURE 5.7.1 b

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FIGURE 5.7.1 c

FIGURE 5.7.1 d

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5.8. Static structural Analysis of concentric springs

Load=165 kg

Material used: beryllium copper and spring steel

Inner spring: beryllium copper

Outer spring: spring steel

FIGURE 5.8

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5.8.1. Modal analysis of concentric springs

FIGURE 5.8.1 a

FIGURE 5.8.1 b

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FIGURE 5.8.1 c

FIGURE 5.8.1 d

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5.9. Graphical Results

Steel vs Beryllium copper

GRAPH 2

Single Spring vs Concentric Springs

Graph 3

-5

0

5

10

15

20

25

30

35

40

45

0 10000 20000 30000 40000 50000 60000

Stress

Nodes

x(steel) y(Berilium copper)

-5

0

5

10

15

20

25

30

35

40

45

0 10000 20000 30000 40000 50000 60000

Stress

Nodes

x(one spring) y(concentric springs)

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6. DYNAMIC ANLAYSIS USING SOLID WORKS

COSMOS Motion is a simulation software package for motion study

of any mechanism. Motion study is a term for simulating and analyzing the

movement of mechanical assemblies and mechanisms. Motion studies are two types;

one is kinematics and the other dynamics. Kinematics is the study of motion without

regard to forces that cause it, and dynamics is the study of motions that result from

forces. Kinematic simulations show the physical positions of all the parts in an

assembly with respect to the time as it goes through a cycle. Dynamic simulation

shows joint reactions, inertial forces.

The traditional method of performing dynamic and kinematic analysis

of any mechanism is preparing the data, solving the algorithms, which involves the

solution of simultaneous equations, and analyzing the results. For a complex

mechanism like vehicle suspension shown in the following Fig 6. Solving the

dynamic equations for motion "by hand" requires intensive calculations, and even

with the help of computerized spreadsheet it may take a few hours to get the results

and plot the graphs. One can develop a program using software to solve the dynamic

equations of motion, but if the geometry of any component changes then the whole

program has to be changed again. A design engineer can successfully overcome

these problems in motion analysis by using COSMOS Motion simulation software.

To analyze the shock absorber using COSMOS Motion, one needs to

know:

1. Each joint in the mechanism will have how many degrees of freedom

2. Spring stiffness and damping force in the shock absorber

3. Which parts are moving and which parts are fixed.

4. Input loads such as normal force, lateral force and longitudinal force.

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6.1. Motion Analysis in Solidworks

The road profile is approximated by a sine wave represented by

q= Y sint Where,

q = Road surface excitation at time t in m.

Y= Amplitude of sine wave = 0.02 m. and

l = Wavelength of road surface = 6 m.

INPUT VARIABLES:

Time=3sec

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Figure 6.1 (a) single degree of damping system

FIGURE 6.1 b

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Analysis of Spring characteristics on an uneven road

Figure 6.1 c

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Responses of model:

GRAPH 4

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GRAPH 5

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7. CONCLUSION

In this project we have modelled shock absorber by using nx7.5.

To validate the strength of the design we have done the structural analysis on shock absorber. We have done analysis by varying

pitch and spring materials i.e., spring steel and beryllium copper.

Also the shock absorber design is modified by adding spring in parallel to the existing spring and structural analysis is done on

shock absorber.

In this paper half bike model is developed for analysis of vibrational effect when it is subjected to harmonic excitation by

road profile.

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8. FUTURE SCOPE

A numerical model using ADAMS has to be developed in order to simulate the dynamic behavior of the shock absorber and to

describe and evaluate its damping coefficient in compression and

rebound cycles.

The design of interchangeable shock absorber test rig has to be developed and fabricated for the dynamics measurement system.

A full vehicle simulation model has to be developed to get better results.

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9. BIBILOGRAPHY

Design of machine elements v.b.bhandari

Patel Quarter Model Analysis of Wagan-R cars Rear Suspension using ADAMS

Mechanical vibrations theory and applications graham Kelly

Comparative Analysis Of Vehicle Suspension

System in Matlab-SIMULINK and MSc-ADAMS with the help of Quarter Car Model

PSG, 2008.DESIGN DATA, kalaikathir achachgam publishers, COIMBATORE, INDIA

Gilles, T. (2005). Automotive Chassis: Brake, Steering & Suspension.: Cencage Learning