International Journal of Engineering Trends and Technology (IJETT) – Volume 27 Number 4 - September 2015
Design of Hydraulic Test Setup to find the Endurance Limit of
Coil/Compression Springs Using Limit Switches
Akshay Kamane, Harshal Vispute, Vardhan Patil, Suraj Shaha, Santosh Katkar
(Students (Former & Current), Department of Mechanical Engineering, Jayawantrao Sawant College of
Engineering, Pune, India)
Abstract— Springs are the fundamentally important
components in a number of real world applications
and hence their design is essentially important.
Frequently according to their applications, the spring
parameters and the working loads and conditions
change and the general factor of safety for design is
quite reasonable with respect to the yield point.
However, a mode of failure which can barely be
predicted without testing is the endurance limit which
takes place due to fatigue failure over repeated
cycles due to fracture patterns occurring in the
springs in allowable working stress ranges and
environmental conditions.
In the present paper, we have designed a hydraulic
set-up based on a mechanism to carry out the
continuous testing of a variety of compression/coil
springs over a large number of work cycles. The use
of limit switches in a hydraulic system to change the
displacement and load on the spring has enabled us
to have more control over long number of working
cycles.
Keywords— Compression/coil springs, Endurance
Limit, Fatigue Failure, Hydraulic Set-up, Design,
Limit Switches.
I.
INTRODUCTION
In order to achieve this, we have used a hydraulic
mechanism using limit-switches and sensors. To have
testing of a large variety of springs, we have taken a
base plate and a spring-support plate on a lead screw.
On this, there rests the actual surface to place and
maintain the spring position. We have taken into
account high cycle fatigue (HCF) to very high cycle
fatigue (VHCF) – over 108 cycles to failure as the
main point of interest in this study. This system has
also been developed so as to get maximum number of
cycles in the minimum possible time with as less
deviation as possible. So overall, it will be a good
option for a variety of applications and be effective.
II.
We have made use of a simple piston and cylinder
arrangement filled with oil. Firstly, the cylinder is
selected according to the amount of stress which
requires to be generated over a wide range. The
design procedure for the piston becomes important
since all other accessories like oil reservoir, vane
pump, suction strainer and a variety of valves are
OEM and are selected according to the required
criteria. The other critical design part is the
supporting bar on which the springs are placed and
tested under the hydraulic system. Components like
the cylinder mounting plate, base plate, compression
ISSN: 2231-5381
The springs manufactured have a wide range of
applications and use somewhat different materials.
Therefore they have different specifications like coil
diameter, wire diameter, spring stiffness, solid length,
free length, spring ends, coatings etc. Consequently it
becomes necessary to have a testing device which
will enable us to have a wide testing range to
accommodate the fatigue testing of various particular
springs. It is also desirable to have high force
application set-up with a fool-proof work rate over
long and continuous cycles.
HYDRAULIC SET-UP
plate, lead screw etc. are also manufactured
according to the specifications. A counter has been
used to measure the cycles. Other pressure sensors
are also used in the system.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 27 Number 4 - September 2015
(KEY:- Bd=bore diameter, Rd=rod diameter,
C=capacity, FR=flow rate, M. pressure=maximum
pressure, FRR=Flow Rate Range, W.
pressure=Working Pressure, lpm=litres per minute.)
III.
HYDRAULIC CIRCUIT
Fig 2.1 CAD model of Hydraulic Set-up
A. HYDRAULIC SYSTEM
SPECIFICATIONS
Sr.
No.
Component
Name
Fig. 2.2 Hydraulic Circuit Diagram with Limit Switches
1.
Cylinder
A1 Model
(Bd=25mm)
(Rd=12.5mm)
2.
Oil Reservoir
T1 Model
(C=40 litres)
3.
Suction
Strainer
S1 Model
(C=38 litres/min)
Vane Pump
P3 Model
(FR=17.6 lpm at 0 bar)
(FR=16.1 lpm at 35 bar)
(FR=14.3 lpm at 70 bar)
4.
Explanation:-
Model No.
Initially, the limit switches are set so as to cover the
full stroke in the cylinder. At normal position (no
stroke) step 1 of the 4/3 solenoid operated DCV is
actuated (by LS 1) where the hydraulic fluid goes
into the cylinder via FCV 1. The piston then moves
forward and touches LS2. This actuates step 3 of the
4/3 solenoid operated DCV and the piston returns to
its original position.
When the system is off (no springs are to be tested),
step 2 of the solenoid operated DCV is in action. If
the pressure build up is too high at this stage, the
fluid is sent back to the reservoir via a pressure relief
valve.
5.
Relief Valve
R2 Model
(FR=19 lpm)
(M. pressure=210 bar)
6.
Flow Control
Valve
F3 Model
(FRR=0-16.3 lpm)
(W. pressure=105 bar)
7.
Direction
Control Valve
D1 Model
(FR=19 lpm)
(M. pressure=350 bar)
8.
Pilot operated
Control valve
P1 Model
(Works till relief valve actuation
begins)
9.
Check Valve
C1 Model
(FR=15.2 lpm)
(M. pressure=210 bar)
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Basically, LS1 operates step 1 of the DCV while LS2
operates step 3. It works similar to a two-way
simultaneous switching system when the system is in
working conditions.
IV.
LITERATURE REVIEW
Jill M. Morgan and Walter W. Milligan, A 1
kHz servo hydraulic fatigue testing system,
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International Journal of Engineering Trends and Technology (IJETT) – Volume 27 Number 4 - September 2015
HCF testing to
109
cycles at
room
hardened and tempered SiCr- and SiCrV-
temperature and 1,000 Hz has been achieved
alloyed valve spring steel and stainless steel.
in the current system for US Air Force.
With a special test strategy in a test run, up
Purushottam Sarjerao Suryawanshi, Prof. T.
to 500 springs with a wire diameter of d =
S. Shikalgar, Swapnil S. Kulkarni, CAE
3.0 mm or 900 springs with d = 1.6 mm
analysis for fatigue failure for coiled spring
were tested simultaneously at different stress
life enhancement in press machine Stamping
levels. Based on fatigue investigations of
operation, Propose new Design and Validate
springs with d = 3.0 mm up to a number of
the Design through trials and testing of the
cycles N = 109 an analysis was done after
Compression Spring for fatigue failure.
the test was continued to N = 1.5 _ 109 and
Mr.
Pharne,
Dr.R.G.Todkar,
their results were compared. The influence
Design,
Analysis
and
of different shot peening conditions were
Fatigue
investigated in springs with d = 1.6 mm.
Behaviour of a Helical Compression Spring
Fractured test springs were examined under
Used for a Two Wheeler Horn, The
optical
experimental results show that at the end of
microscope (SEM) and by means of
3 lakh cycles, no cracks or breakages were
metallographic micro sections in order to
found in any of the five modified springs
analyse the fracture behaviour and the
under experimental investigation.
failure mechanisms. The paper includes a
V.Kazymyrovych, Very high cycle fatigue
comparison of the results of the different
of
paper
spring sizes, materials, number of cycles and
examines the development and present
shot peening conditions and outlines further
status of the Very High Cycle Fatigue
investigations in the VHCF-region.. For
(VHCF)
engineering
comparison the results for the springs with d
materials. The concept of ultrasonic fatigue
= 1.6 mm and d = 3.0 mm and Ps = 98% are
testing is described in light of its historical
summarised in. Except for springs made of
appearance covering the main principles and
the stainless steel wire, the fatigue strength
equipment variations.
of springs with d = 3.0 mm is higher than for
Supriya Burgul, Literature Review on
springs with d = 1.6 mm. The size effect
Design, Analysis and Fatigue Life of a
would imply higher fatigue strength for
Mechanical Spring, Vol.2, July 2014, Long-
smaller wire diameters.
term fatigue tests on shot peened helical
T. Udomphol, Fatigue Testing, Mechanical
compression springs were conducted by
Metallurgy Laboratory, The fatigue strength
means of a special spring fatigue testing
of engineering materials is in general lower
machine at 40 Hz. Test springs were made
than their tensile strength. A ratio of the
of three different spring materials – oil
fatigue strength to the tensile strength as
J.
J.
Dr.N.D.Sangle,
Experimental
engineering
Validation
for
materials,
phenomenon
in
this
microscope,
scanning
electron
described in equation 1 is called the fatigue
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International Journal of Engineering Trends and Technology (IJETT) – Volume 27 Number 4 - September 2015
ratio. It is normally observed that, in the
Selecting Minimum efficiency = 87 %
case of steels, the fatigue strength increases
in
proportional
to
the
tensile
Efficiency of Cylinder = 1 -
stress.
Therefore, improving the tensile strength by
0.87 = 1 -
hardening or other heat treatments normally
increases the fatigue strength of the material.
V.
= 0.065
DESIGN CALCULATIONS
a.
kN
Total Friction Force = 0.065 kN
Selection of Cylinder:-
b.
Determination of Piston Rod Diameter
and Length:-
Selecting A1 Model, Bore Diameter= 25mm, Rod
Diameter= 12.5mm
This set up designed with equal velocities for
(Taking initial force= 125 N.)
extending and retracting of piston,
We know that,
Pressure=
So,
=
d = 0.2 D to 0.3 D
= 1018591.63 N/m2
(D = Diameter of Piston)
= 10.18 bar
i.
Efficiency of Cylinder:For easy Installation and Rigidity,
ncylinder = 1 ≤ 20
Where,
Piston Rod Diameter (d) = 0.2 D to 0.3 D
Fs = Static Force = 490.5 N = 0.490 KN
= 12.5 mm
As we know that,
Checking Ratio,
Expected efficiency of various hydraulic cylinders is:
≤ 20
1) For normal cylinder = 0.94 to 0.95
≤ 20
2) For telescopic cylinder = 0.88 to 0.90
8 ≤ 20 ……..Design is Safe
Also, Efficiency of hydraulic cylinder is also found to
vary with diameter of piston as seen below:
c.
Diameter of Piston (mm)
Efficiency of Cylinder
20 to 50
80-85
50 to 120
85-90
Above 120
90-95
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Selection of Components:Considering Flow Velocities,
Consider 75 RPM (75 Rev/Min)
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International Journal of Engineering Trends and Technology (IJETT) – Volume 27 Number 4 - September 2015
So, Total flow velocity = Total distance in 1
cycle = 0.5 m
Fc =
Here,
I=
Velocities are constant for extending and
retracting = 0.5 m/sec
=
Q = Area * Velocity
= * (0.025)2 * 0.5
= 1.19 * 10-9 m4
= 2.4543*10-4 m3/sec
Fc =
Q = 14.7262 lpm
So, Oil Reservoir = 3 * lpm = 3 * 14.7262
= 44.18 litres.
d.
Fc = 24664 N
Maximum permissible load on piston rod,
FOS = 5 (General Cylinder)
Design of Piston Rod:-
F=
Material Stainless Steel
E = Modulus of Elasticity = 210 GPa
=
Selecting if it is Short Column or Long
F = 4932.8 N
Column,
As our force on piston rod is 4932.8 N,
which is greater than 500 N.
< 10 …………Short Column
Fapplied˂Fallowable ………………Design is Safe
>10………Long Column
e.
In our case, L = 0.2 m, d = 0.0125 m
Design of Supporting bar:Material C25Mn75
General purpose: low stress component
Syt= 274.68 N/
> 10
FOS=2
16 > 10 ………… So Long Column
Maximum shear stress theory:
According to Euler’s Formula,
Fc =
le =
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τ = syt/2
=137.34 N/
σallowable = 137.34/2
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International Journal of Engineering Trends and Technology (IJETT) – Volume 27 Number 4 - September 2015
Condition (One end is fixed one end is
=68.67 N/
free)
Load On bar = 15 Kg = 147.15 N
σallowable
68.67
dsb = 8.76*10-3 m
dsb = 1.6676 mm
So, Selecting diameter for supporting bar = 50
For Buckling:
mm.
VI.
SIMULATION
GRAPH
(TO
DETERMINE BEHAVIOUR OF THE
TESTING MACHINE)
magnitude of the spring deflection in each cycle. This
provides a rough idea of the actual behaviour of the
system and makes it possible to get the best possible
output from the system.
VII.
QUOTATION FOR BOUGHT OUT
PARTS’ (O.E.M.)
a) Power Pack:Supplier Name: Delta Hydraulics,
Bhosari Midc, Pune
Total Cost: Rs.35000 only.
b) Hydraulic Cylinder:Supplier Name: Delta Hydraulic,
(Graph 1)
Bhosari Midc, Pune.
AXES:-
Total Cost: Rs.6000 only.
x= time (0-50 is 1 cycle and all further intervals
are of 50);
c)
Make:
y= deflection of spring (mm).
Type: 8 Digit Display
Explanation:-To have a thorough understanding of
how the actual hydraulic set-up will work, we have
carried out a simulation on CATiA. The parameters
like force applied, stroke of the piston and efficiency
of the hydraulic system and the spring specifications
are considered as the input parameters. The
behaviour of the spring deflections within endurance
limit is plotted on the graph. 2 constraints are
considered as the individual cycle-time per one
forward and return stroke of the piston and the
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Counter:-
Specification: 0 to 8 Digit counting
Cost: Rs.4500 only.
d) Miscellaneous Components:Sensors: Rs.1000 only.
Hoses and Fittings: Rs.1000 only.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 27 Number 4 - September 2015
VIII.
COST ANALYSIS/ESTIMATION
Sr. No.
Description
Cost (Rs.)
1.
Bought out cost
51835
2.
Process Cost
8000
3.
Installation cost
4500
4.
Miscellaneous cost
2800
Total Cost
67135
IX.
XI.
FUTURE SCOPE
This mechanism can be modified to check
the behaviour of springs (within endurance
limit) over a wide range of applications
(medium and heavy).
Testing time can be reduced by having a
timed relay in addition to the limit switches
in a circuit with connections to the solenoid
operated flow control valve.
Locking of the mechanism as well as
holding the springs in place while testing
them can be achieved by designing the lead
screw as a power screw & applying the
locking conditions of a hydraulic jack.
EXPECTED OBSERVATIONS
XII.
Parameters
REFERENCES
Hydraulic System
1.
Cycles Time
Nisbett, Shigley’s Mechanical Engineering Design, McGraw-
75
(Cycles/min)
“Mechanical Spring”, Richard G. Budynas and J. Keith
Hill, Ninth Edition.
Velocity (m/s)
0.50
2.
Enhancement in Press Machine Stamping Operation”,
Time Required for
testing 1 spring (10
“CAE Analysis for Fatigue Failure for Coiled Spring Life
Purushottam Sarjerao Suryawanshi1, Prof. T.S.Shikalgar2,
4 Days
Swapnil S. Kulkarni3, International Journal of advanced
lakh cycles)
Engineering Research and Studies, April-June 2014 (61-63).
Return of Investment
3.
134 Days
“Fatigue”, ASM international Elements of Metallurgy and
Engineering Alloys, 2008.
4.
X.
“A 1 KHz Servo Hydraulic Fatigue Testing System”, Jill M.
Morgan and Walter W. Milligan, Conference in “High cycle
CONCLUSION
fatigue of structural materials”, 1997 (305-312).
Thus, we have designed a robust, fast, reliable and
less maintenance centric hydraulic coil-spring set-up
to test the endurance limit of compression springs.
This can be used over a long number of cycles for
various springs. Standard parts are used and a packed
(air-tight) hydraulic system is made. (After every
usage, bleeding of the circuit to remove air-bubbles is
suggested). High viscosity index oil is suggested to
be used since the system has a long repeated cycle
which will lead to heating of the oil. (Around ISO
VG 46)
Hence, the system we have designed is fool-proof in
nature, albeit a bit expensive. This system will truly
revolutionize the concept of continuous testing of coil
springs.
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5.
“Design, Analysis and Experimental validation for fatigue
behaviour of Helical Compression Spring used for Two
Wheeler Horn ”, Mr. J.J.Pharne1, Dr. R.G.Todkar2, Dr.
N.D.Sangle3, IOSR Journal of Mechanical and Civil
Engineering, Vol. 11, Issue 6 , Nov-Dec 2014 (05-11).
6.
“Literature Review on Design, Analysis and Fatigue Life of a
Mechanical Spring”, Supriya Burgul, International Journal of
Research in Aeronautical and Mechanical Engineering,
Vol.2, July 2014.
7.
“Design Data Book”, PSG Edition, 1978.
8.
www.springer.com
9.
“Fluid Power with Applications”, Anthony Esposito,
Pearson, III.
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