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Design, Modeling and Design, Modeling and Optimization of Two Optimization of Two Wheel Rear Shock Wheel Rear Shock

AbsorberAbsorber

By By

K . Suresh KumarK . Suresh Kumar

Internal Guide

A.Siva Rama Krishna,Associate Professor,SNIST.

External Guide

G.Malakondaiah (M.Tech),Mechanical HOD of St.Mary’s Engg.College.

Designing of Spring Designing of Spring according to Load applied.according to Load applied.

Load is 275 Kg.Load is 275 Kg.

Modeling of Springs & Shock Modeling of Springs & Shock Absorbers by using Catia Absorbers by using Catia

Software.Software.

Catia V5 Release 19.Catia V5 Release 19.

Analysis of Shock Absorber Springs & Analysis of Shock Absorber Springs & Assembly of its parts by using Ansys 10.0 Assembly of its parts by using Ansys 10.0 SoftwareSoftware..

• In Analysis we are using 275 Kgs Load.In Analysis we are using 275 Kgs Load.• Here conducting Static & Model Analysis.Here conducting Static & Model Analysis.• Static Analysis is used for finding Stresses & Static Analysis is used for finding Stresses &

Displacement.Displacement.• Model Analysis is used for finding Mode Shapes.Model Analysis is used for finding Mode Shapes.• Presently materials used for springs is Spring Presently materials used for springs is Spring

Carbon Steel.Carbon Steel.• But in this project we are using Beryllium Copper But in this project we are using Beryllium Copper

Material.Material.

OBJECTIVE:OBJECTIVE:

• The design of spring in suspension system is very The design of spring in suspension system is very important. In this project a shock absorber is designed and important. In this project a shock absorber is designed and a 3D model is created using Catia V5. The model is also a 3D model is created using Catia V5. The model is also changed by changing the diameter of the spring.changed by changing the diameter of the spring.

• Structural analysis and modal analysis are done on the Structural analysis and modal analysis are done on the shock absorber by varying material for spring, Spring Steel shock absorber by varying material for spring, Spring Steel and Beryllium Copper. The analysis is done by considering and Beryllium Copper. The analysis is done by considering loads, bike weight, single person and 2 persons.loads, bike weight, single person and 2 persons.

• Structural analysis is done to validate the strength and Structural analysis is done to validate the strength and modal analysis is done to determine the displacements for modal analysis is done to determine the displacements for different frequencies for number of modes.different frequencies for number of modes.

• Comparison is done for two materials to verify best Comparison is done for two materials to verify best material for spring in Shock absorber.material for spring in Shock absorber.

1.INTRODUCTION1.INTRODUCTION::

A shock absorber or damper is a mechanical device A shock absorber or damper is a mechanical device designed to smooth out or damp shockdesigned to smooth out or damp shock impulse, and dissipate impulse, and dissipate Kinetic energy.Kinetic energy.

Pneumatic and hydraulic shock absorbers commonly Pneumatic and hydraulic shock absorbers commonly take the form of a cylinder with a sliding piston inside.take the form of a cylinder with a sliding piston inside.

The shock absorbers duty is to absorb or dissipate The shock absorbers duty is to absorb or dissipate energy. One design consideration, when designing or choosing energy. One design consideration, when designing or choosing a shock absorber, is where that energy will go. In most a shock absorber, is where that energy will go. In most dashpots, energy is converted to heat inside the viscous fluid. dashpots, energy is converted to heat inside the viscous fluid. In hydraulic cylinders, the hydraulic fluid will heat up, while in In hydraulic cylinders, the hydraulic fluid will heat up, while in air cylinders, the hot air is usually exhausted to the air cylinders, the hot air is usually exhausted to the atmosphere. In other types of dashpots, such as atmosphere. In other types of dashpots, such as electromagnetic ones, the dissipated energy can be stored electromagnetic ones, the dissipated energy can be stored and used later. In general terms, shock absorbers help and used later. In general terms, shock absorbers help cushion cars on uneven roads.cushion cars on uneven roads.

2.APPLICATIONS2.APPLICATIONS::

ShockShock absorbers are an important part of automobile absorbers are an important part of automobile

and motorcycle suspensions, aircraft landing gear, and the and motorcycle suspensions, aircraft landing gear, and the

supports for many industrial machines. Large shock absorbers supports for many industrial machines. Large shock absorbers

have also been used in structural engineering to reduce the have also been used in structural engineering to reduce the

susceptibility of structures to earthquake damage and susceptibility of structures to earthquake damage and

resonance. A transverse mounted shock absorber, called a resonance. A transverse mounted shock absorber, called a

yaw damper, helps keep railcars from swaying excessively yaw damper, helps keep railcars from swaying excessively

from side to side and are important in passenger railroads, from side to side and are important in passenger railroads,

commuter rail and rapid transit systems because they prevent commuter rail and rapid transit systems because they prevent

railcars from damaging station platforms.railcars from damaging station platforms.

3. SHOCK ABSORBER TYPES:3. SHOCK ABSORBER TYPES:

There are a number of different methods of There are a number of different methods of

converting an impact /collision into relatively converting an impact /collision into relatively

smooth cushioned contact.smooth cushioned contact.

3.1. Metal Spring 3.1. Metal Spring

3.2. Rubber Buffer 3.2. Rubber Buffer

3.3. Hydraulic Dashpot 3.3. Hydraulic Dashpot

3.4. Collapsing safety Shock Absorbers 3.4. Collapsing safety Shock Absorbers

3.5. Pneumatic Cylinders 3.5. Pneumatic Cylinders

3.6. Self compensating Hydraulic 3.6. Self compensating Hydraulic

3.1. Metal Springs:3.1. Metal Springs:

Simply locating metal springs to absorb the impact Simply locating metal springs to absorb the impact

loads are a low cost method of reducing the collision speed loads are a low cost method of reducing the collision speed

and reducing the shock loading.  They are able to operate in and reducing the shock loading.  They are able to operate in

very arduous conditions under a wide range of very arduous conditions under a wide range of

temperatures.  These devices have high stopping forces at temperatures.  These devices have high stopping forces at

end of stroke. Metal springs store energy rather than end of stroke. Metal springs store energy rather than

dissipating it.dissipating it.

3.2. Elastomeric Shock absorbers: 3.2. Elastomeric Shock absorbers:

Elastomeric dampers are very widely used because of Elastomeric dampers are very widely used because of

the associated advantages of low cost and mould ability the associated advantages of low cost and mould ability

together with performance benefits. These low cost options for together with performance benefits. These low cost options for

reducing the collision speed and reducing the shock loading reducing the collision speed and reducing the shock loading

and providing system damping.   and providing system damping.  

3.3. Hydraulic Dashpot:3.3. Hydraulic Dashpot:

This type of shock absorber is based on a simple This type of shock absorber is based on a simple hydraulic cylinder.  As the piston rod is moved hydraulic fluid hydraulic cylinder.  As the piston rod is moved hydraulic fluid is forced through an orifice which restricts flow and is forced through an orifice which restricts flow and consequently provides a controlled resistance to movement of consequently provides a controlled resistance to movement of the piston rod.the piston rod.

On completion of the stroke the system is stable - the On completion of the stroke the system is stable - the energy being dissipated in the hydraulic fluid as heat.  This energy being dissipated in the hydraulic fluid as heat.  This type of shock absorbers are provided with springs sufficient to type of shock absorbers are provided with springs sufficient to return the actuator to its initial position after the impacting return the actuator to its initial position after the impacting load is removed. load is removed.

3.4. Collapsing Safety Shock Absorbers:3.4. Collapsing Safety Shock Absorbers:

These are single use units which are generally specially These are single use units which are generally specially designed for specific duties.  They are designed such that at designed for specific duties.  They are designed such that at impact they collapse and the impact energy is absorbed as impact they collapse and the impact energy is absorbed as the materials distort in their inelastic/yield range. the materials distort in their inelastic/yield range.

3.5. Air (Pneumatic) Springs:3.5. Air (Pneumatic) Springs:

These devices use air as the resilient medium . Air has These devices use air as the resilient medium . Air has a high energy storage capacity compared to metal or a high energy storage capacity compared to metal or elastomer materials. elastomer materials.

Due to the compressibility of air these have a sharply rising Due to the compressibility of air these have a sharply rising force characteristic towards the end of the stroke. The force force characteristic towards the end of the stroke. The force on an air cylinder buffer is determined by the relationship PVon an air cylinder buffer is determined by the relationship PVnn = constant.= constant.

Air springs require more maintenance than metal or Air springs require more maintenance than metal or elastomer based springs.elastomer based springs.

3.6. Self compensating Hydraulic:3.6. Self compensating Hydraulic:

Self compensating hydraulic devices are similar to the Self compensating hydraulic devices are similar to the hydraulic dashpot type except that a number of orifices are hydraulic dashpot type except that a number of orifices are provided allowing different degrees of restriction throughout provided allowing different degrees of restriction throughout the stroke. These type of shock absorbers are provided with the stroke. These type of shock absorbers are provided with springs sufficient to return the actuator to its initial position springs sufficient to return the actuator to its initial position after the impacting load is removed. after the impacting load is removed.

4. DEFINITION OF A SPRING:4. DEFINITION OF A SPRING:

A spring is defined as an elastic body, whose A spring is defined as an elastic body, whose function is to distort when loaded and to recovers function is to distort when loaded and to recovers its original shape when the load is removed. It is a its original shape when the load is removed. It is a device that changes its shape in response to an device that changes its shape in response to an external force, returning to its original shape when external force, returning to its original shape when the force is removed. The energy expended in the force is removed. The energy expended in deforming the spring is stored in it and can be deforming the spring is stored in it and can be recovered when the spring returns to its original recovered when the spring returns to its original shape. Generally, the amount of the shape change shape. Generally, the amount of the shape change is directly related to the amount of force exerted. If is directly related to the amount of force exerted. If too large a force is applied, however, the spring will too large a force is applied, however, the spring will permanently deform and never return to its original permanently deform and never return to its original shape.shape.

5. RAW MATERIALS OF A SPRING:5. RAW MATERIALS OF A SPRING:

Steel alloys are the most commonly used spring materials. Steel alloys are the most commonly used spring materials. The most popular alloys include high-carbon (such as the music wire The most popular alloys include high-carbon (such as the music wire used for guitar strings), oil-tempered low-carbon, chrome silicon,used for guitar strings), oil-tempered low-carbon, chrome silicon, chrome vanadium, and stainless steel.chrome vanadium, and stainless steel.

Other metals that are sometimes used to make springs are Other metals that are sometimes used to make springs are beryllium copper alloy, phosphor bronze, and titanium. Rubber or beryllium copper alloy, phosphor bronze, and titanium. Rubber or urethane may be used for cylindrical, non-coil springs. urethane may be used for cylindrical, non-coil springs.

1. Plain Carbon Steel of 0.9 to 1.0% of carbon is a common 1. Plain Carbon Steel of 0.9 to 1.0% of carbon is a common material for springs. material for springs.2. Steel with 0.85 to 0.95% Carbon & 0.3 to 0.4% Manganese 2. Steel with 0.85 to 0.95% Carbon & 0.3 to 0.4% Manganese is is used for longer sized springs. used for longer sized springs.3. Alloy Steels such as Chrome – Vanadium and Silicon – 3. Alloy Steels such as Chrome – Vanadium and Silicon – Manganese Steels are used for better grade Manganese Steels are used for better grade

springs.springs.4. Chromium Steel, Beryllium Copper and Monel metal (Nickel 4. Chromium Steel, Beryllium Copper and Monel metal (Nickel Alloy) can also be used in special cases to increase Alloy) can also be used in special cases to increase

Fatigue Fatigue resistance (endurance limit), corrosion resistance (endurance limit), corrosion resistance and resistance and Temperature resistance. Temperature resistance.

6.TYPES OF SPRINGS:6.TYPES OF SPRINGS:

Springs are used in a wide range of types & Sizes.Springs are used in a wide range of types & Sizes.6.1. Helical Springs 6.1. Helical Springs 6.2. Leaf or Laminated Springs.6.2. Leaf or Laminated Springs.

6.1. HELICAL SPRINGS:6.1. HELICAL SPRINGS:

The coil or helical spring consists of a wire or rod The coil or helical spring consists of a wire or rod wound into a helix and is primarily intended for axial direct wound into a helix and is primarily intended for axial direct compression on tension load.compression on tension load. Helical Springs may be further classified as:Helical Springs may be further classified as:

A. Close – Coiled Helical Springs, and A. Close – Coiled Helical Springs, and B. Open – Coiled Helical Springs.B. Open – Coiled Helical Springs.

A. Close – Coiled Helical Springs: A. Close – Coiled Helical Springs: In Close – Coiled Helical In Close – Coiled Helical Springs, the angle of helix is less than 10° i.e., the pitch Springs, the angle of helix is less than 10° i.e., the pitch (distance between the similar points on the adjacent coils of (distance between the similar points on the adjacent coils of the Springs) .the Springs) .

B. Open – Coiled Helical Springs: B. Open – Coiled Helical Springs: In Close – Coiled Helical In Close – Coiled Helical Spring is very small as compared to Open – Coiled Helical Spring is very small as compared to Open – Coiled Helical Spring. Spring.

7.MECHANICAL PROPERTIES OF SPRING MATERIALS:7.MECHANICAL PROPERTIES OF SPRING MATERIALS:  7.17.1 Strength:Strength: It is the ability of a material to resist the It is the ability of a material to resist the externally applied forces without breaking or yielding. The externally applied forces without breaking or yielding. The Internal resistance offered by a part to an externally applied Internal resistance offered by a part to an externally applied force is called Strength.force is called Strength.

7.2 Stiffness:7.2 Stiffness: It is the ability of a material to resist It is the ability of a material to resist deformation under stress. The modulus of rigidity is the deformation under stress. The modulus of rigidity is the measure of stiffness.measure of stiffness.

7.3 Ductility:7.3 Ductility: It is the property of a material enabling it to be It is the property of a material enabling it to be drawn into wire with the application of a tensile force. A drawn into wire with the application of a tensile force. A Ductile material must be both strong & plastic. The ductility is Ductile material must be both strong & plastic. The ductility is usually measured by the terms, percentage of elongation and usually measured by the terms, percentage of elongation and percentage of reduction in area. The ductile materials percentage of reduction in area. The ductile materials commonly used in engineering practice are Mild Steel, Copper, commonly used in engineering practice are Mild Steel, Copper, Aluminum, Nickel, Zinc, Tin & Lead.Aluminum, Nickel, Zinc, Tin & Lead.

7.4 Resilience:7.4 Resilience: It is the property of a material to absorb It is the property of a material to absorb energy and to resist shock and impact loads. It is measured by energy and to resist shock and impact loads. It is measured by the amount of energy absorbed per unit volume within elastic the amount of energy absorbed per unit volume within elastic limit. This property is essential for spring materials.limit. This property is essential for spring materials.

7.5 Creep:7.5 Creep: When a part is subjected to a constant stress at When a part is subjected to a constant stress at high temperature for a long period of time, it will undergo a high temperature for a long period of time, it will undergo a slow and permanent deformation called creep. This property is slow and permanent deformation called creep. This property is considered in designing internal combustion engines, boilers considered in designing internal combustion engines, boilers and turbines.and turbines.

7.6 Fatigue:7.6 Fatigue: When a material is subjected to repeated When a material is subjected to repeated stresses, its fails at stresses below the yield point stresses. stresses, its fails at stresses below the yield point stresses. Such type of failure of a material is known as Fatigue.Such type of failure of a material is known as Fatigue.

MANUFACTURING PROCESS OF SPRINGSMANUFACTURING PROCESS OF SPRINGS

1. Coiling / Windinga. Cold windingb. Hot Winding

2. Hardeninga. Heat Treating

3. Finishinga. Grindingb. Shot Peeningc. Settingd. Coatinge. Packaging

4. Quality Control

Beryllium CopperBeryllium CopperIt is a copper base alloy containing about 97.75% copper and

2.25% Beryllium. It has high yield point, high fatigue limit and excellent cold and hot corrosion resistance. It is particularly suitable material for springs, heavy duty electrical switches, cams & buildings. Since the wear resistance of Beryllium copper is five times that of Phosphor bronze.

The Helical Springs are either cold formed or Hot formed depending upon the size of the wire. Wires of small sizes (less than 10mm Dia) are usuallywound cold whereas larger size wires are wound hot. The strength of the wires varies with size, smaller size wires have greater strength and less ductility, due to the greater degree of cold Working.

Beryllium copper is available in the normal wrought forms of sheet, strip, wire, tube, rod, bar and forgings, and also as castings made by sandMoulding or by one or other of the modern precision techniques.

DEFINITIONS OF SPRINGS:DEFINITIONS OF SPRINGS:1. SPRING INDEX: It is the ratio of mean coil diameter to the diameter of the spring wire.

Spring Index, C = D/d.

2. STIFFNESS: It is defined as the load per unit deflection.

Stiffness (Spring Constant or Spring Rate) K = W/∂

3. HELIX ANGLE: It is the angle which the axis of the spring wire makes with horizontal line

Perpendicular to the axis of the spring.

4. SOLID LENGTH: It is the length of the spring measured along the axis when the spring is

completely compressed i.e., the coils are touching each other.

Solid Length (Ls) = n.d

5. FREE LENGTH: It is the length of the spring measured along the axis when the spring is

unloaded.

Free Length of the spring (Lf)= n .d+ ∂max +0.15 ∂max

Free Length may also be obtained from the equation.

Lf = n.d + ∂max + (n-1) x 1mm

6. PITCH:6. PITCH: The axial distance between adjacent coils in uncompressed state is called pitch. The axial distance between adjacent coils in uncompressed state is called pitch.

Pitch of the coil, P = Free Length/ (n-1)Pitch of the coil, P = Free Length/ (n-1)

7. SPRING RATE: 7. SPRING RATE: Every spring configuration has a spring rate, “k” defined as slope of its force-Every spring configuration has a spring rate, “k” defined as slope of its force-

deflection curve. If slope is constant, it is a linear spring, anddeflection curve. If slope is constant, it is a linear spring, and

k = F/y k = F/y where: F is applied force, and y is slope.where: F is applied force, and y is slope.

DESIGN CALCULATIONS FOR HELICAL DESIGN CALCULATIONS FOR HELICAL SPRINGS OF A SHOCK ABSORBERS SPRINGS OF A SHOCK ABSORBERS

(Material : BERYLLIUM COPPER)(Material : BERYLLIUM COPPER)

Mean diameter of a coil = D=62mm

Given Data:

Diameter of wire d = 8mm

Total no of coils n1 = 18

Height “h” = 220mm

Outer diameter of spring D0 = D +d =70mmNo of active turns n = 14

G = 41000 = modulus of rigidity

Weight of bike = 125 Kgs

Let weight of 1 person = 75 Kgs

Weight of 2 persons = 75 x 2 = 150 Kgs

Weight of bike + persons = 275KgsWeight of bike + persons = 275Kgs Rear suspension = 65% Rear suspension = 65% 65% of 275 = 179Kgs 65% of 275 = 179Kgs Considering dynamic loads it will be double Considering dynamic loads it will be double W = 358Kgs = 3512N W = 358Kgs = 3512N For single shock absorber weight = w/2= 1756N For single shock absorber weight = w/2= 1756N = W= W We know that, We know that,

compression of spring (δ) =compression of spring (δ) = 8W x C8W x C3 3 x nx n G x d G x d C = spring index = D/d = 62/8 = 7.75 = 8 C = spring index = D/d = 62/8 = 7.75 = 8 (δ) = (δ) =

SPRING OF A SHOCK ABSORBER:SPRING OF A SHOCK ABSORBER:

Total Assembly of a Shock AbsorberTotal Assembly of a Shock Absorber

Total Assembly of a Shock Absorber in Total Assembly of a Shock Absorber in Pro-ePro-e

SpringSpring SteelSteel::

Beryllium CopperBeryllium Copper

Conclusion:Conclusion: In our project we have designed a shock absorber used in a 150cc bike.

We have modeled the shock absorber by using 3D parametric software CATIA. To validate the strength of our design, we have done structural analysis and modal analysis on the shock absorber by applying 275kgs load on shock absorber. We have done analysis by varying spring material Spring Steel and Beryllium Copper. By observing the analysis results, the analyzed stress values are less than their respective yield stress values. So our design is safe. By comparing the results for both materials, the stress value is less for Spring Steel than Beryllium Copper.

ResultsResults

•So we can conclude that as per our analysis using material Spring steel for spring is best.

Thank YouThank You