IAS SRFP2012Final Report

IAS SRFP-2012 Final Report Page 1

IAS Summer Research Fellowship Programme 2012

Final Report

____________________________________________________

ELECTROPNEUMATIC BAR MANIPULATION SETUP

FOR COMPRESSION KOLSKY BAR APPARATUS

____________________________________________________

Author:

Debraj Roy

Applicant No. ENGS1933

B.Tech (M & AE) IV Semester

Amity School of Engineering & Technology, Jaipur

Under the guidance of

Prof. Krishna Jonnalagadda

(Department of Mechanical Engineering)

Indian Institute of Technology Bombay, Powai

Report Due Date:

30 July 2012


Abstract

An experimental setup has been developed for the compression Kolsky bar

(split-Hopkinson pressure bar or SHPB) apparatus at IIT Bombay to be duly used

for high strain-rate (103

s-1

) testing at elevated temperatures (up to 1000°C). The

setup constitutes of an electro-pneumatic bar actuator to bring the two bars in the

apparatus in contact at the moment the strain wave reaches the input bar. An

electric relay with timed delay setup implements the momentary contact between

the bars & synchronizes the contact with the strain wave. The setup presented is

easily producible and simplified from existing setups. It would greatly negate any

chance of formation of thermal gradients among the bars upon contact with

specimen at high temperature and hence, reduce the errors in the study of dynamic

behavior of materials at elevated temperatures.


Acknowledgements

I would like to extend my heartiest gratitude to respected Prof. Krishna

Jonnalagadda, Department Of Mechanical Engineering, IIT Bombay for his

visionary guidance and sizable subvention at each and every step of the project. It

was his precisionist & rationalist remonstrance that obscured the way for me to

work through this programme and develop an apical precinct for the task. It was

extremely amiable experience to work under a truly devoted and ingenious

scholastic at one of the most reputed institutes of India.

Also, it would be malefic of me if I fail to extend my gratitude to all the

colleagues whom I interacted in the time being of 8 weeks. I would immensely like

to appreciate the support of Vignesh Pai, Nikhil Madame, Subir Patra & Mr. Vinod

Pare for their generous & receptible nature throughout the work.

The fact that this small journey is approaching its end is sorrowful for me as

I would have liked to gain more from all the aforementioned delightful personnel. I

was also willing to have completed with the fabrication of the setup from my own,

but shortage of time and material requisites have hindered my willingness. It would

be grateful of me to lend my hand in nearby future for any other task in the project

and even experiment on it once it is completed.


Table of Contents

Abstract………………………………………………………………………….2

Acknowledgements……………………………………………………………...3

Table of Contents………………………………………………………………..4

Figures…................................................................................................................6

Tables……………………………………………………………………………8

1. Introduction…………………………………………………………….9

2. Historical Perspectives to Bar Manipulator Setups…………………...10

a. Circulating Boiling Water………………………………………...10

b. Impedance Matching Insulators…………………………………..10

c. Screw Driven Bar Mover system…………………………………11

d. Electro-pneumatic Bar manipulator Setup……………………......11

3. Bar Manipulator Setup – Description……………………………........12

4. Components & Computational Validation for the Bar Manipulator

setup…………………………………………………………………..16

a. Pressure Pipes……………………………………………………..16

b. Computational validation for pipe diameter………………………16

c. Computational validation for pipe thickness……………………...17

d. Computational validation for stresses in pipe…………………......18

e. Wall-mount accessory for pipes…………………………………...18

i. U-type Pipe Clamps………………………………………....18

ii. U-Bolt Pipe clamps………………………………………….19

f. Ball Valve…………………………………………………………20

g. Connectors for setup………………………………………………22

i. Threaded fittings…………………………………………….23

ii. Push-in Straight Reducing Connectors……………………...23

iii. Push-in T-Connectors……………………………………….24

h. Solenoid Valve……………………………………………………24

i. Pressure Regulator with Gauge- Relieving Type…………………27

j. Air Receiver…………………………………………………….....29

k. Computational validation for cylinder thickness…...……………..32


l. Mounting Bracket for Air Receiver……………………………..…32

m. Relay Circuit…………………………………………………….....34

n. Pusher Ring………………………………………………………...37

o. Actuator Block with stand………………………………………....41

p. Characteristics for compressed N2 at 8 bar………………………...43

q. Computational validation for Reynold’s No. using pipe of 10mm

∅…………………………………………………………..……..…44

r. Computational validation for compressed N2 flow rate using pipe of

10mm ∅…………………………………………………………….45

s. Pressure Drop Calculations for a sample 2m pressure pipe……….46

t. Theoretical Validation for Bar Manipulator Setup Working…...…47

u. Optimization with reduced impact for Bar Manipulator Setup……48

5. References……………………………………………………………50

6. Bibliography………………………………………………………….52


Figures

Figure 1: Electro-pneumatic Bar Actuator setup for High temperature Compression

Kolsky Bar experiment……………………………………………………………12

Figure 2: Pneumatic Circuit for Electro-Pneumatic Bar Manipulator Setup……15

Figure 3: U-type Pipe Clamps CATIA V5 Part Model....……………………….18

Figure 4: U-type Pipe Clamps CATIA V5 Working Views Draft………………19

Figure 5: U-Bolt Pipe Clamps CATIA V5 Part Model………………………….19

Figure 6: U-Bolt Pipe Clamps CATIA V5 Working Views Draft……………….20

Figure 7: Ball Valve CATIA V5 Surface Model…………………………………20

Figure 8: Ball Valve Section Cut view[v]………………………………………..21

Figure 9: Ball Valve CATIA V5 Working Views Draft……………….................22

Figure 10: Threaded Fittings [ix]………………………………………………….23

Figure 11: Push-in Straight Reducing Connectors CATIA V5 Surface Model

[16]…………………………………………………………………………23

Figure 12: Push-in T-Connectors CATIA V5 Surface Model [17]………………24

Figure 13: Solenoid Valve CATIA V5 Surface Model…………………………25

Figure 14: Solenoid Valve CATIA V5 Working Views Draft………………….25

Figure 15: Pneumatic Symbol for 3/2-way Solenoid Valve Normally Open……26

Figure 16: Pressure Regulator with Gauge………………………………………28

Figure 17: Air Receiver 2.5L 2D-CAD Drawing……………………………….30

Figure 18: Air Receiver CATIA V5 Part Model…………………………………31

Figure 19: Air Receiver CATIA V5 Working Views Draft……………………..31


Figure 20: Mounting Bracket for Air Receiver CATIA V5 Part

Model……………………………………………………………………………...32

Figure 21: Mounting Bracket for Air Receiver CATIA V5 Working Views

Draft………………………………………………………………………………33

Figure 22: ON-Delay Relay Pneumatic Circuit Diagram…………………..........34

Figure 23: ON-Delay Relay Electrical Circuit Diagram………………………..35

Figure 24: Time v/s Operating Voltage plot for ON-Delay relay………………35

Figure 25: Terminal setup connections for ON-Delay Relay……………………36

Figure 26: View of terminals of ON-Delay Relay………………………………37

Figure 27: View of terminals of ON-Delay Relay………………………………37

Figure 28: Pusher Ring Type 1 CATIA V5 Part Model…………………………38

Figure 29: Pusher Ring Type 1 CATIA V5 Working Views Draft……………..39


Figure 31: Pusher Ring Type 2 CATIA V5 Working Views Draft………………40


Figure 33: Pusher Ring Type 3 CATIA V5 Working Views Draft………………41

Figure 34: Actuator Block with stand CATIA V5 Part Model……………….…42

Figure 35: Actuator Block with stand CATIA V5 Working Views Draft ……..43

Figure 36: Reynold’s No. Calculations………………………………………….44

Figure 37: Flow Rate calculations…………………………………………….….45

Figure 38: Pressure Drop Calculations…………………………………………..46

Figure 39: Free Body Diagram for the setup……………………………………47


Tables

Table 1: PUN-H Pressure Tubing specifications [13, iii]………………………..…..16

Table 2: Ball Valve, manually actuated specifications [15, iii]…………………..….21

Table 3: Bill of Materials - Ball Valve, manually actuated [15, iii]…………………22

Table 4: Solenoid Valve, 3/2-way, Normally Open specifications [18, iii, VI]….....…26

Table 5: Bill of Materials - Solenoid Valve, 3/2-way, Normally Open [18, iii, VI]…..27

Table 6: Pressure Regulator with Gauge- Relieving type specifications [19]….......28

Table 7: Bill of Materials - Pressure Regulator with Gauge- Relieving type [19]….28

Table 8: Air Receiver specifications……………………………………………...29

Table 9: Mounting Bracket for Air Receiver specifications……………………....33

Table 10: ON-Delay relay specifications [20]………………………………….......36

Table 11: Pusher Ring specifications……………………………………………..38

Table 12: Actuator Block with stand specifications..……………………………..42


Introduction

“High Temperature Compression Kolsky Bar” is a modification from

general Kolsky bar setup which is also widely known as the “Split Hopkinson

Pressure Bar”. This apparatus is used primarily for the testing of dynamic behavior

of the material at elevated temperature at high strain rates. It was built with the aim

of assuring material’s dependability and usefulness under conditions involving

impacts. The Universal Testing Machine can work well for the quasi-static loading

conditions and up to strain rates of 0.1 s-1

but for when deciding for any structural

component which has to undergo immense amount of strain at various strain rates

of the order of up to 103s

-1 at high temperatures, the quasi-static results just don’t

prove to be pleasing to any point and so the high strain rate testing using the

Kolsky bar setup is preferred for solving the purpose [1]

.

Various high strain rate testing methods have been devised over the time

being using the setup starting from John Hopkinson, his son Bertram Hopkinson

and by other eminent contributors RM Davies and H. Kolsky. The prevalent

Kolsky bar setup measures stress pulse propagation in a metal bar by using two

Hopkinson bars in series, known as the split-Hopkinson bar with cathode-ray

oscilloscopes to record the pressure wave propagation in the bars.

The compression apparatus is found to allow high strain rate deformation at

dynamic equilibrium of sample or as usually said, when stress gradient is found to

be zero. When the same setup is applied to specimen testing at high temperature it

is often referred to as “High Temperature Dynamic Recovery Test” [2]

. It involves

heating of a specimen prior to being sandwiched between the incident and the

transmission bar while a projectile strikes the incident. For this the bar have to be

kept particularly at low temperatures or else it has been observed that the specimen

temperature drops when it is in contact with the bars, & along with this thermal

gradients are formed in bars which greatly affects the elastic properties of the bars

and consequently the stress pulses. In a few cases, there may also be chance of


annealing of bar ends. In an attempt to reduce the “Cold Contact Time” [3]

, a basic

approach preferred, is to heat the specimen without keeping it in contact with the

bars [3, 4]

or else innumerous variations for the elastic modulus and wave velocities.

Another way would be to use short length insulating impedance-matched ceramic

bar [5]

but requirement o large input energy for heating the specimen negates use of

this method. The setup to be designed required the precise timing for the contact of

the bars which would anyways cause thermal gradients to be developed. This

report describes the setup being in process of being built at IIT Bombay for the

high temperature compression Kolsky bar experiment. The bar manipulator setup

would be an electro-pneumatic actuation system with a timed relay for optimized

bar closure once the incident wave arrives.

Historical perspective to Bar Manipulator Setups

Circulating Boiling Water [6]

This setup was able to heat specimen to 100°C using a chamber circulating

boiling water only which didn’t affect the wave propagation.

Impedance Matching Insulators [7]

This setup used aluminum oxide bars impedance matched to the incident &

transmitted bars on both sides of the specimen inside the heating furnace and were

seen to increase error rates on account of the change in impedance of aluminum

oxide bars with high temperature.

Another similar setup using Tungsten Carbide inserts impedance matched

with the bars were used in an experiment for attaining temperatures up to 1000°C

and strain rates of 1650 s-1

upon HSLA-65 specimen.[8]


Screw Driven Bar Mover system [9]

This bar mover was primarily a screw driver with opposing threads on each

end which were driven by an electric motor using a chain link. The screw driver is

connected to the bars using two arms of which the one attached to the transmitter

bar triggers a positioned switch made of photodiode so that they are relayed to the

striker so that the bars are brought to contact 50-150 ms prior to the compression

wave entering the specimen. A 5°C decrease in the specimen temperature was

observed as expected for 400ms cold contact time.

Electro-pneumatic Bar Manipulator Setup

This setup particularly supersedes others due to greater compatibility for

working upon both conducting & non-conducting materials when using the

infrared spot heaters as done by Lennon & Ramesh [3]

with a much easily

obtainable coordination between firing of gas gun and connecting of bars with the

specimen. Alternatively, an electro-pneumatic setup had been made with a

pneumatic system moving the specimen inside the furnace & removing it at test

temperature & finally aligning it with the bars [10]

.

The ease of manipulation of the method has increased interest of the

researchers all over the world to employ this efficient, reliable and creative setup.

With an aim of bringing the cold contact time below 50ms [11]

where most systems

without synchronized heating setups have a CCT of 500ms, the setup has been

designed in accordance to attain the prevalent standards achievable by the available

means of present time. In this method particularly, maximum attainable

temperature depends upon the transfer mechanism which must be as quick &

accurate as possible so as to reduce contact to as less as the smallest fraction of a

second.


Bar Manipulator Setup – Description

FIG. 1


A schematic of the whole setup designed to fulfill the need of bar

manipulation enabling high temperature compression testing is been given in the

previous page.

The two bars, namely the incident & the transmitted bars of length nearly

1300cm are being used in the setup which would remain elastic throughout the

experiment & would have the small cylindrical specimen at a minute distance from

contact or say air gap somewhere in between them approximating a distance of 2-

5mm. The projectile fired by the gas gun would strike one end of the incident bar

once the spot heater heats up the specimen to the test temperature. A thermocouple

wire would serve the purpose of suspending the specimen while it is being heated

till the incident wave would arrive. The incident & transmitted would be brought in

contact a few ms prior to the arrival of the incident wave by triggering off the bar

manipulator setup. The specimen would be moved along with the incident to the

direction of application of air pressure and thus eventually it would be sandwiched

between the bars or may be placed in the aluminum catcher tube as of ease.

The electro-pneumatic bar actuator used to move the bars in contact would

be triggered of after a particular delay ranging from 5ms - 1s once the pressure is

being given to the gas gun. This is achieved by a pressure switch which would

convert the pressure at the input pipe to an electrical signal. This signal is then sent

to an ON-Delay relay designed especially for solving the purpose as the

commercially available timed relays have operating range of 250ms to 60min. The

explanation for the internal design of the setup of relay is been mentioned at

further stage of the report.

Simultaneously, the main pressure source would be used to charge this

electro-pneumatic actuator setup thus eradicating requirement of an independent

pressure source. For this, a T-connection in the main pipe leading to the gas gun

was been implemented with a ball valve in the design. The ball valve is a shut-off

valve primarily designed to open or close the flow manually, working of which has

also been detailed in the later part of the report. Thus, a manual control on the

auxiliary setup for high-temperature testing of materials was kept in mind

increasing alterability of the setup to varied experimentation modes.


When the ball valve is let open high pressure input N2 starts rushing to an

auxiliary air chamber or as referred afterwards as the air receiver and so a pressure

regulator is used in the setup reducing the pressure to a desirable pressure of 8

bars. A manometer or gauge attached to the regulator helps in attaining the desired

pressure. The computations for deciding the desired pressure is been mentioned in

later sections. A normally open 3/2-way electrical-directional control valve also

popularly known as the “Solenoid valve” is been used in the next step to allow the

filling of the pressurized gas in the air receiver.

Once the gas gun is been fired and the pressure switch has been triggered it

would cause the solenoid valve to close thus allowing flow through the alternative

path through the outlet pipe. Thus, the high pressure gas for the air receiver would

start to move through outlet pipe & would start evacuating the air receiver. A

regulator at outlet pipe would regulate pressure at the final stage before the air is

delivered to the actuator block. A pressure up to 5 bar would be suggested to get

the optimum results without damaging any portion of the setup depending upon the

need. As for the flow rate is concerned maintaining continuity at all the sections of

pipe and considering the pipe losses, a suggested flow rate of 0.5-0.6 liters per

second or in standard units 30-36 liters per minute would e sufficient to meet the

cause. Validation of these is been done in the computational section[i]

.

Directing the output high pressure is been sent to a covering or as preferably

said as actuator block. This covering is cylindrical in shape with a countersunk

hole and the end where pressure is passed to encase a pusher ring within it. This

can be made up of polyisoprene or synthetic rubber like styrene-butadiene for its

cost-efficiency and natural shock absorbing tendency once high pressure air would

start to act. As suitable a wide range of polymer or even wood can serve as the

constructing material. The pusher ring made up of commercially available SS304

steel would be placed inside the actuator block as per desired extent. This ring

would drag along with it the incident bar to come in contact with the specimen

under effect of the high pressure gas with the liberty to slide inside the covering.

When desired displacement in the block has been achieved the ring escapes out of

the covering thus allowing the high pressure gas to escape to the atmosphere. A

pneumatic circuit of the CAD schematic for the bar manipulator setup has been

given in the following page.


The distance to be travelled by the pusher ring before it escapes the actuator

block would be varied according to the speed of the projectile so as to negate with

any impact occuring between incident bar and specimen, i.e, conserve momentum

upto optimum extent. The further travel of the transmitted bar from the specimen

and incident bar would be prevented using a paper strip which would be torn but

would successfully stop the overtravel. With the bars successfully closed, the

projectile should have struck the incident bar by now and would send the incident

wave. Thus a very minute cold contact time can be ensured with the setup being

designed with even great scope for manipulation as per need.

FIG. 2

Pneumatic Circuit for Electro-Pneumatic Bar Manipulator Setup


Components & Computational Validation for the Bar

Manipulator setup

Pressure Pipes

Commercially available pipes were being under consideration for use in the

setup. Length of the pipe is negotiable as per purpose. NPT connection at pipe ends

would greatly ease out task of push-in connections. The PUN-H (polyurethane)

pipes is highly suitable for compressed air but has weak resistance to flame and

isn’t a suitable antistatic agent as it supports buildup of static charge. A suitable

resistance to hydrolysis, media & cleaning agents is seen in these pipes.

Feature PUN-H Tube

Material Polyurethane

Tubing O.D. 10 mm

Nominal Pipe Size 1/8 in

Threads per Inch 27

Thread Pitch 0.03704 in (0.94082 mm)

Operating Pressure 0.95 to 10 bar

Operating Temperature -35°C to +60°C [13,iii]

Computational validation for pipe diameter[14]

Length of incident bar, L = 1.3m =1300mm

Diameter of incident bar, D = .5”= 12.7mm

Volume of incident bar, V = 2

4

D L =1.6468x10

-4 m

3

Density of incident bar material, 𝛒 = 7.8x103 kg/m

3

Mass of incident bar, M = 𝛒V = 1.2845 kg

Table 1: PUN-H Pressure Pipe Specifications


Diameter of pusher ring, d = 50mm

Thickness of pusher ring, t = 5mm

Volume of pusher ring, v = 2

4

d t = 9.817477x10-6 m3

Mass of ring, m =0.07657632 kg

Mass of the manipulation system, Ms = 1.361076 kg +

Coefficient of friction for metal contact, μ = 0.3 (approx.)

Estimated force for overcoming friction, Ff = μMsg = 4.005647 N

Maximum velocity attainable by striker bar, Vs = 70 m/s (assumption)

Length of barrel for striker bar, Ls = 1.25m

Time taken by striker bar, Ts =s

s

L

= 17.857 ms

Flow rate from source, Q = 0.5 l/s = 5x10-4

m3/s (assumption)

Max. time for bringing bar in contact with a min. delay Tmax = 15ms

Distance of air gap between bars, S = 4mm (assumption)

Min. velocity of manipulation system, Vmin =S

T= 0.26667 m/s

Applied pressure from source, P = 5 bar

Density of N2 at 5 bar, 𝛒N = 8.91216 kg/m3

Mass flow rate of N2, dmN= Q𝛒N = 4.4506x10-3

kg/s

Applying Law of conservation of momentum

Max. velocity of N2 through pipes, VN = mins

N

VM

dm = 9.0306 m/s

Critical diameter for pipe, dpipe= 4

N

Q

V= 8.396157 mm

Henceforth, PUN-H polyurethane pipe diameter “dpipe” selected is “10mm”.

Computational validation for pipe thickness

Tensile strength for PUN-H pipe, t = 28 MPa


Weisbach constant for PUN-H pipe, c = 0.2mm

Critical thickness for pipe tc = d

2

pipe

t

P

+c = 0.28928 mm

Henceforth, PUN-H polyurethane pipe thickness “tpipe” selected is

“0.3mm”.

Computational validation for stresses in pipe

Outer radius of pipe, ro = 5mm

Inner radius of pipe, ri = ro -t = 4.7 mm

Lame’s Equation for Tangential Stress, t = 2

2 2

0

i

i

Pr

r r(

2

0

21

r

x )

On outer surface, x=ro, mint = 7.591065 MPa

On inner surface, x=ri, maxt = 8.0910653 MPa

Wall-Mount Accessory for Pipes

Opt.1 U-type Pipe Clamps

High quality stainless steel sheet

is generally used for these

clamps with the surface

galvanised for long term wear &

corrosion resistance. M10

clamps spaced at 20cm is under

consideration to solve the task as

the high pressure flowing

through pipes is turbulent

enough to cause circumferential

motion in the PUN-H pipes.

FIG. 3


Opt.2 U- Bolt Pipe clamps

FIG. 5

FIG. 4

U-type Pipe Clamps CATIA V5 Working Views Draft


Ball Valve

FIG. 7

FIG. 6

U-Bolt Pipe Clamps CATIA V5 Working Views Draft

Ball Valve CATIA V5 Surface Model


For the purpose of setting up the bar manipulator setup active the ball valve

is been used. The above CATIA V5 model is a replica of FESTO QH[15,iii]

2/2 way,

manually actuated ball valve with G1/2 threads for pneumatic connection with a

capacity to handle flow rates upto 84,000 l/min. The spherical ball alias “seat”

present in the valve stops the flow. Moving the lever or as generally said handle,

the sphere rotates about presenting the face with a cutout section allowing the flow

of fluid. The extent to which the lever is rotated decides the amount of fluid to

flow.

[v]

Feature Ball Valve, manually actuated

Weight 340 g

Nominal Size 15 mm

Actuation Torque 8 Nm

Type of Mounting In-line installation

Sealing principle Soft


Ambient Temperature -20°C to +180°C

FIG. 8

Ball Valve Section Cut view

Table 2: Ball Valve, manually actuated specifications


Ball Valve, manually actuated Material

Housing Brass

Lever Painted aluminum

Ball Hard chrome plated

Seals PTFE

[15,iii]

Connectors for setup

Opt.1 Threaded fittings

Also termed as reducing nipple, these nickel-plated brass fitting reduce

connect two pneumatic components of varying diameters. It may be used to

FIG. 9

Table 3: Bill of Materials - Ball Valve, manually actuated

Ball Valve CATIA V5 Working Views Draft


connect the pipes to solenoid valve as well as the ball valves to the PUN-H

pipes & probably the pressure regulators as per material purchased for the

fabrication of setup.

[ix]

Opt.2 Push-in Straight Reducing Connectors

[16]

These connectors can be used as an alternative to the previous threaded fitting

as they support push-in feature suitable for pipes and usable with compressed air.

FIG. 10

FIG. 11

Threaded Fittings

Push-in Straight Reducing Connectors CATIA V5 Surface Model


The ends of the connector have varying diameters. Nitrile rubber sealing provides a

perfect seal between the standard outer diameter tubing and the body of the fitting.

Opt.3 Push-in T- Connectors

The robust stainless steel retaining claws within the fitting hold the tubing

securely without damaging its surface while absorbing vibrations and surges.

Simple push-in connections with rotatabilty improve ease of work. This would be

essentially used to deviate a portion of pressure from the main supply to the setup

while one end allows the flow to the gas gun.

[17]

Solenoid Valve

This valve acts as an interface between the tasks of switching off air supply to

air receiver from pressure source and vacating the pressure air from air receiver to

the actuator block.[17]

FIG. 12

Push-in T- Connectors CATIA V5 Surface Model


FIG. 13

FIG. 14

Solenoid Valve CATIA V5 Surface Model

Solenoid Valve CATIA V5 Working Views Draft


If no current is applied to the solenoid coil of the directional control valve,

the pressurized gas from main pressure source flows to the air receiver.

Here, the solenoid coil is de-energised and inactive.

If current is applied to the solenoid coil, the directional control valve

switches and the input to the air receiver is stopped and the pressurized gas

moves out of air receiver to the actuator block.

In any case of interrupting the current, the valve switches back. The inlet

opens and the gas flows into air receiver.

[17]

In initial position, the working port 2 is linked to pressure port 1 by the slot

in the armature.

If the solenoid is energised, the magnetic field forces the armature up against

the pressure of the spring. The upper sealing seat opens and the path is free

for flow to exhaust port 3 from working port 2. The lower sealing seat

closes, shutting off the path between port 1 and port 2.

If the solenoid coil is deenergised, the armature is retracted to its initial

position by the return spring. The path between port 1 and port 2 is opened

and the path between port 2 and port 3 is closed. The compressed air is

vented via the pipe at port 3.

Feature Solenoid Valve Normally Open

Function 3/2-way

FIG. 15

Pneumatic Symbol for 3/2-way Solenoid Valve Normally Open

Table 4: Solenoid Valve, 3/2-way, Normally Open specifications


Version In-line valve

Voltage 12V dc/ 230V ac

Reset Method Pneumatic spring

Sealing Principle Soft

Nominal Size 2.1 mm

Standard Nominal Flow Rate 200 l/min

Width 10 mm

Switching Time on/off 12/10 ms

Pneumatic Connection M5

Type of Mounting Via through holes



Electrical connection Horizontal plug

Manual Override Pushing

Type of Control Piloted

Solenoid Valve Normally Open Material

Housing Aluminum

Seals Nitrile Rubber (BUNA-N)

[18,iii,vi]

Pressure Regulator with Gauge- Relieving Type

The pressure regulator to be used as per recent developments in the project

status involved secondary ventilation that helps maintaining a constant operating

pressure despite fluctuations in line pressure & the amount of air consumed. The

relieving type regulator signifies reduction of output pressure. Adjustments to the

input pressure to the air receiver and at the output before the actuator block are

been made possible by the pressure regulator. The regulator would be mounted on

the wall using a small cardboard or wooden panel, that can bear the load of the

regulator fixed to the wall using screws. Mounting brackets are to be used for

fixing the regulators with the regulators.

Table 5: Bill of Materials - Solenoid Valve, 3/2-way, Normally

Open Specifications


[vii]

Feature Pressure Regulator

Type 16 bar with gauge

Design Diaphragm regulator

Mounting Using mounting brackets

Connection ½” NPT

Nominal Flow Rate 3500 l/min

Operating Pressure 1 to 16 bar


Weight 0.78kg

Pressure Regulator Material

Housing Gadolinium-Zinc

Seals Nitrile Rubber (BUNA-N)

Adjustment Knobs Nylon 6 (Polycaprolactam)

[19]

FIG. 16

Table 6: Pressure Regulator with Gauge- Relieving type specifications

Open Specifications

Table 5: Pressure Regulator with Gauge

Table 7: Bill of Materials - Pressure Regulator with Gauge- Relieving type

Open Specifications


Air Receiver

This is the back bone of the setup which enables storing & simultaneous release

of the high pressure N2. The specifications for the air receiver are:

Feature Air Receiver

Outer Diameter 100mm

Length of Cylinder 300mm

L/D Ratio 3

Thickness of Cylinder 3mm

Volume 2.3562 L

Mounting Using Mounting Brackets

Operating Pressure 1 to 8 bar

Max. Permissible Pressure 15 bar

Diameter of Inlet Valve 1/4”

Material Used SS304

Weight of Cylinder 18.378317 kg

Table 8: Air Receiver specifications


FIG. 17


FIG. 18

FIG. 19

Air Receiver CATIA V5 Part Model

Air Receiver CATIA V5 Working Views Draft


Computational validation for cylinder thickness[14]

Outer diameter of cylinder, D = 100mm

Length of cylinder, L = 300mm

Volume of cylinder, V = 2

4

D L = 2.359x10

-3 m

3

Safe stress for SS304 pressure vessel, t = 30 MPa

Max. permissible pressure for cylinder, P = 15 bar

Critical thickness for cylinder, tc = 2 t

PD

= 2.5 mm

Also, Lame's Equation, t = 2

d( 1t

t

P

P

) =2.56575mm

Henceforth, thickness for pressure vessel of SS304 steel is 2.5mm.

Mounting Bracket for Air Receiver

An optional mounting bracket for wall mounting the air receiver has been

designed which is similar to the supports used for fire extinguishers.

Mounting Bracket

CATIA V5 Part

Model

FIG. 20


Feature Mounting Bracket

Material Used SS304

Length 330mm

Outer Diameter for brackets 105mm

Thickness 3mm

No. of mounting screws 6

Dist. b/w adjacent screws 50mm from top

FIG. 21

Mounting Bracket CATIA V5 Working Views Draft

Table 9: Mounting Bracket for Air Receiver specifications


Relay Circuit

The above is the circuit diagram of Relay. It acts as the signal processing

unit providing a direct control on the flow of air into the air receiver. The used type

for the bar manipulator setup is an ON-Delay Timed relay which works as follows;

The main pressure source switched on would allow the high pressure gas to run to

the gas gun. A pressure switch placed right before the T-connector to deviate the

flow to the auxiliary setup would send an electrical signal to mark that the main

setup has started. It marks that the striker has been fired and now it’s time to bring

the bars in contact. As it’s generally believed that the striker would take longer

time to incident bar so a small delay has to be given for starting the solenoid valve

considering a start-off time for the valve. The electrical equivalent for the relay is

given next.

FIG. 22

ON-Delay Relay Pneumatic Circuit Diagram


When pressure switch S1 is pressed on starting flow from main pressure

source, an input voltage say U is set up & the relay gets energized and time

delay begins.

The output remains de-energized during timing and at end of time delay,

output energizes. Relay contacts R change state after time delay is complete.

Reclosing the pressure switch during timing resets time delay. Any loss of

voltage would reset the time delay & output.[20]

The following is a time v/s

operating voltage general characteristics curve for ON-Delay Relay

[20]

FIG. 23

Time v/s

Operating

Voltage for

ON-Delay

Relay

FIG. 24

ON-Delay Relay Electrical Circuit Diagram


Feature ON-Delay Relay

Type Electromechanical relay

Accuracy 10%

Reset Time 50ms

Recycle Time 150ms

Load Type DPDT or SPDT

Panel Mounting Using 11 pin plug-on socket with brackets

Operating Voltage 230V ac 15%

Operating Current 10A ac

Indicator Timing LED to mark relay energised

Range 8ms to 60s

2ms increments from 8ms to 200ms

300ms increments from 100ms to 60s

Min. Setting 5% of range, except 5ms on 8ms range

Repeat accuracy 0.1% or

5ms whichever is greater

Housing Impact resistant plastic case [20]

The relay terminals of standard ON-Delay relays are been provided below

which depict the various pins on board for connections.

FIG. 25

Table 10: ON-Delay relay specifications

Terminal setup connections for ON-Delay Relay


Pusher Ring

The small ring attached to the incident bar that would move the whole bar along

with it when pressure is applied upon it is been designed in 3 ways which could be

FIG. 26

FIG. 27

View of terminals of ON-Delay Relay

View of terminals of ON-Delay Relay


manufactured as found desirable. Standard SS304 stainless steel pusher rings

commercially available can be used as per specifications.

Feature Pusher Ring

Material Used SS304

Inner Diameter 12.705mm

Outer Diameter 50mm

Thickness 5mm

Opt.1

This type of pusher ring is compatible for low operating pressure . This

would have less contact with the bar but would prevent easy escape of pressurized

air due to its geometric construction until it itself escapes the covering. It would

have more region in contact with the covering. It’s inner region thickness is

supposedly taken as 3 mm in above CATIA V5 model.

FIG. 28

Table 11: Pusher Ring specifications

Pusher Ring Type 1 CATIA V5 Part Model


Opt.2

FIG. 29

FIG. 30

Pusher Ring Type 1 CATIA V5 Working Views Draft



This type of pusher ring would maximise contact with the bar and would

easily drag the bar along with itself due to increased friction without chance of

slipping off. It would be recommended to be used when operating pressure is high

and distance to be covered is less as compared to general cases. The outer region

thickness is taken as 2mm while rest configuration is taken for dimensions in table.

Opt.3

FIG. 31

FIG. 32




This is a slightly modified version of pusher ring that could be used in case the

momentum of bars is found to be greater than calculated. In such case the cutout

regions along the circumference of the ring would allow easy escape of high

pressure gas even when in contact with the covering and limit the pressure force

acting on the ring. Thus the bar would move slowly and will take a bit more time

for bar closure. The outer region has 2mm thickness and the slope geometry ends

at the inner region of 5mm thickness.

Actuator Block with stand

FIG. 33



The actuator block is preferably made of nitrile rubber so that a better grip

can be attained with the bar or else the high pressure air may cause back

draft upon the actuator block and push it backwards. A stand with screws for

fixing the actuator block upon the base of the Kolsky bar setup has been

designed. This would allow the block to readily absorb any vibrations from

the PUN-H pipes due to the high pressure N2. The holes made in the actuator

block are for housing the pipes which have NPT threads at end.

Feature Air Receiver

Outer Diameter 80mm

Inner Diameter 50mm

Material Nitrile Rubber

Stand Base dimensions 200mmx2mmx1.5mm

Stand Clamp O.D./I.D. 95mm/82mm

Stand material SS304

Diameter/ Spacing for Stand rods 5mm/20mm

Actuator Block with Stand CATIA V5 Part Model FIG. 34

Table 12: Actuator Block with stand specifications


Characteristics for compressed N2 at 8 bar[ix]

Density, 𝛒N = 8.91216 kg/m3

Specific heat capacity, Cp = 1.05248 kJ/kg K

Specific heat capacity, Cv = 0.744924 kJ/kg K

Dynamic viscosity, ν = 2.28396x10-6

m2/s

Kinematic viscosity, μ = 2.0327245 x10-5

Pa-s

K-factor for PUN-H pipes, K = 0.140

Minor losses coefficient for PUN-H pipes, Km = 26 [Iix]

Pipe roughness for PUN-H pipes, kr =0.082mm

Actuator Block with Stand CATIA V5 Working Views Draft

FIG. 35


Computational validation for Reynold’s No. using 10mm Φ

pipe[viii]

Friction factor, fD = 64

eR= 0.00296087

FIG. 36


Computational validation for compressed N2 flow rate using

pipe of 10mm dia

[viii]

FIG. 37


Pressure Drop Calculations for a sample 2m pressure pipe

p = 2

2D

L Vf

D

[viii]

FIG. 38


Theoretical Validation for Bar Manipulator Setup Working

Mass of Manipulation System+, Ms = 1.361076 kg

Coefficient of friction for metal contact, μ = 0.3 (approx.)

Angle of friction, θ = tan-1

μ = 16.69924°

Outer diameter of pipe, Dpipe = 10 mm

Inner diameter of pipe, dpipe = 3/8” =9.525 mm (assumption, may vary)

Area of effective pressure, Apipe = 2

id

4

P pc= 7.125574x10-3 m3

Pressure applied on actuator block, P = 5 bar

Applied force at output, F = P x A = 35.62787 N

For 2 pipe system, Feff = 2F =71.25574 N

Net friction force developed in the system, Ff = μ(F sinθ + mg) = 10.1482

N

Accelerating force for manipulator system, Fnet = Feff – Ff =61.10754 N

Acceleration of manipulator system, a = netF

m= 44.8965 m/s2

Initial velocity of manipulator setup, u = 0m/s

Distance of travel for setup, s = 4mm (assumption)

Minimum time required for striker to reach barrel end, ts = 17.857 ms

Applying Newton’s IInd

equation

FIG. 39


S = ut + 0.5at2

t = 0.5

s

a = 13.3487 ms

Lowest delay required, td =4.5083 ms

Optimisation with reduced impact for Bar Manipulator Setup

I. At s = 1mm

v = 2as = 0.2996548 m/s

t = s

V=3.337 ms

Stopping distance, sstop = 2

2 g

v

=

2

5.886

v = 15.255 mm

Net distance travelled, stotal = 16.255 mm

II. At s = 0.5mm

v = 2as = 0.211888 m/s

t = s

v=18.878 ms


2 g

v

=

2

5.886

v = 7.62768 mm


III. At s = 0.25mm

v = 2as = 0.1498274 m/s

t = s

v=26.697 ms


2 g

v

=

2

5.886

v = 3.81384 mm



So, the system would show effective working of bringing the bars in closure

even if the pusher ring is 0.25mm within the actuator block. The momentum

delivered to the ring would still bring the bars in closure. For all greater values, a

paper stop to trap the momentum is been suggested.


References

1. Song, B. & Weinong Chen, Split Hopkinson (Kolsky) Bar Design, Testing

and Applications. Springer Science + Business Media, LLC 2011

2. Nemat-Nasser S, Introduction to High Strain Rate Testing, ASM Metals

Handbook, Vol 08, University of California, San Diego

3. Lennon, A.M. & Ramesh, K.T. (1998) A Technique for Measuring the

Dynamic Behavior of Materials at High Temperatures. International Journal

of Plasticity, 1998. 14: p. 1279-1292.

4. Nemat-Nasser S, Isaacs JB. Direct measurement of isothermal flow stress of

metals at elevated temperatures & high strain rates with application to Ta &

Ta-W alloys. Acta Materialia 1997; 45:907-19

5. Rosenberg, Z., Dawicke, D., Strader, E., Bless, S.J., A new technique for

heating specimens in split-Hopkinson-bar experiments using induction –coil

heaters, Exp. Mech. September, 275-278 (1986)

6. Krafft, J.M., Sullivan, A.M., Tipper, C.F. The effect of static and dynamic

loading and temperature on the yield stress of iron and mild steel in

compression. Proc. Roy. Soc, London A221, 114-127 (1954)

7. Lindholm, U. and L. Yeakley, High strain-rate testing: Tension and

compression. Experimental Mechanics, 1968. 8(1): p. 1-9.

8. Shazly, M., V. Prakash, and S. Draper, Mechanical behavior of Gamma-Met

PX under uniaxial loading at elevated temperatures and high strain rates.

International Journal of Solids and Structures, 2004. 41(22-23): p. 6485-

6503

9. Frantz, C. E. , P. S. Follanshee, and W.J.Wright, New Experimental

Techniques with the Split Hopkinson Pressure Bar, 8th International

Conference on High Energy Rate Fabrication June 17-21, 1984, San Antonio

10. Apostol, M., T. Vuoristo, and V.-T. Kuokkala, High temperature high strain

rate testing with a compressive SHPB. J. Phys. IV France, 2003. 110: p.

459- 464.

11. Li, Y., Yazhou Guo, Haitao Hu , Q. Wei, A Critical Assessment of High-

Temperature Dynamic Mechanical Testing of Metals, International Journal

of Impact Engineering 36 (2009). p. 177–184.

12. Dike, Shweta (2010), Dynamic Deformation of Materials at Elevated

Temperatures, Thesis (M.S.) under Dr. Vikas Prakash & Dr. John


Lewandowski, Department of Mechanical & Aerospace Engineering,

CWRU.

13. FESTO Tubing/Fitting Combination PUN-H Product Catalogue, Festo AG

& Co. KG

14. Khurmi, R.S., Machine Design, Eurasia Publishing House (Pvt.) Ltd.2005

15. FESTO Ball Valves QH, QHS Product Catalogue, Festo AG & Co. KG

16. FESTO Plug sockets and push-in connectors Product Catalogue, Festo AG

& Co. KG

17. Prede, G. & D. Scholz, Electropneumatics (Basic Level), Festo Didactic

GmbH & Co., D-73770 Denkendorf 2002

18. FESTO Valve series VOVG Product Catalogue, Festo AG & Co. KG

19. FESTO Regulator LR - Basic Version Product Catalogue, Festo AG & Co.

KG

20. Delay on Break (Release) TDBL, TDB, TDBH Digi-Set Time Delay Relay,

ABB Inc. Low Voltage Products & Systems Sales Information Catalogue.

21. Minilec Monitoring Relays Product Catalogue, Minilec Corporations


Bibliography

i. www.pipeflowcalculations.com

ii. www.engineeringtoolbox.com

iii. www.festo.com

iv. www.wikipedia.com

v. http://www.franklinvalve.com/images/BallValve.gif

vi. http://www.solenoidvalvesuk.com

vii. www.indiamart.com

viii. www.pipeflowcalculations.com

ix. www.engineeringtoolbox.com

http://www.pipeflowcalculations.com/

http://www.engineeringtoolbox.com/

http://www.festo.com/net/SupportPortal/Downloads/12852/PSI_416_16_en.pdf

http://www.wikipedia.com/

http://www.franklinvalve.com/images/BallValve.gif

http://www.solenoidvalvesuk.com/

http://www.indiamart.com/

http://www.pipeflowcalculations.com/

http://www.engineeringtoolbox.com/

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