Coventry University: Literature Review of Springs, Seals & Rubber

This literature review explores the properties and applications of springs, mechanical seals, and rubber in mechanical engineering. It discusses different types of springs, including open-coil helical springs and their end configurations, along with the materials used in their manufacturing, such as steel alloys and ceramic materials. The review also examines mechanical seals, focusing on PTFE seals and their mechanical properties, highlighting their applications in industrial settings and advantages like long life and low maintenance. Furthermore, it delves into the characteristics of rubber, including natural rubber and various synthetic types like Styrene-Butadiene-Rubber and Silicone Rubber, detailing their properties and uses. The document provides a concise overview of these essential components in mechanical systems, with relevant references. Desklib provides solved assignments and study materials for students.

Literature review:
Spring:
A spring is an elastic object which stores mechanical energy. Usually, springs are made of spring
steel material. The spring design is classified according to materials, mechanical properties and
application of mechanical equipment.
Spring coil classified as following:
Open-coil helical springs: the open helical springs offer resistance to the externally applied load
along the axis of spring. This types of spring have constant coil diameter. The compression
springs are the most energy-efficient storage devices. They spring regains its original shape after
releasing the load. The spring can classify as per the ends types. This may be classified with
ends such as closed end (square end), closed ground ends, Double closed ends, open ends.
Closed and squared ends: the closed and squared ends compression helical springs have an
equal pitch at the intermediate section and get reduced at both ends. The ends remain squared
and closed because it keeps stands or vertical position such as a base of spring.
Closed and ground springs: Closed and ground springs ends have high slenderness ratio which
can withstand vertically on the flat surface. This types of springs with ends types are used for
highly accurate or precision application.
Double Closed: The closed ends and double closed end springs both are works similar. But
double closed ends spring are squared end configuration. These compression springs have two
closed coils at the end. If the compression spring consists high slenderness ratio, it becomes
more risk of buckling. For this case, the double closed ends configuration proposed stability in
the spring.
Open Ends: the open ends compression spring suggest the constant pitch which does not vary
throughout the wire. The entire coils have a specific pitch in between them because of the open
end type. This types of springs with the open ends require inserted into the hole or fixed over the
round bar, shaft or mandrel.
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A raw material for manufacturing springs:
The steel alloys are usually used for spring materials. The alloys used in manufacturing are
carbon, oil-tempered low carbon steel, chromium silicon, stainless steel and chrome vanadium at
the surface of spring steel. The ceramic material used for coil spring at the considerable high-
temperature. The glass fiber composite materials are used for manufacturing spring with stainless
steel alloy.
The manufacturing process used for spring:
The Coiling, hardening, Finishing are the principle manufacturing process of the manufacturing
spring steel. For coiling process, the wire up to 18 to 20 mm diameter can be used can coil at the
moderate temperature using principle techniques. This can be done through the specific spring
winding machine, lathe machine or another special application machine. If lath machine used for
spring, then lead screw on the lathe must be used in order to align the wire with the require pitch
as it wraps surrounds the mandrel. (B.GDemczy, et.al. 2002)
Further hot winding and heat treatment process have used for the spring manufacturing process.
At the ends of process finishing have done through grinding, shot peening, coating, heat
treatment, packaging etc. (Cheryl Y, et, al. 2002)
Table.1 Mechanical properties of spring steels:
Materials ASTM
Designation
Modulus of
Rigidity ( G)
psi
Youngs
Modulus ( E)
psi
Density
lb/❑3
Maximum
Temperature
F
Stainless
steel- 302
A313 10^7 28 x 10^7 0.287 600
Stainless
Steel 316
A313 10^7 28 x 10^7 0.287 600
Stainless
steel 17-7PH
A313 11 x 10^6 29.5 x 10^6 0.285 750
Brass B134 50 x 10^7 16 x 10^6 0.318 220
Chromium
silicone
A231 11 x 10^7 30 x 10^7 0.295 480
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Inconel X750 B637 11 x 10^7 31 x 10^7 0.299 1150
Chrome
Vanadium
A232 11 x 10^7 30 x 10^7 0.284 480
Beryllium
Copper
B197 7x 10^7 1.85 x 10^7 0.298 400
Phosphor
Bronze
B159 6.25 x 10^6 1.5 x 10^7 0.32 220
Hard Drawn A227 11.5 x 10^7 3 x 10^7 0.285 250
Mechanical Seal:
The mechanical seal is a device which keeps the mechanical system together by preventing
leakage between two temporary joints. It is usually used in pump, pressure vessel and that kind
of device where liquid or fluid is essential to use for operation. The mechanical seal contains
pressure, without contamination etc. The material is joined between through seal and its
effectiveness depends on the types of adhesive used for sealing and pressure applied between
two joint. It also depends on the compression of the gaskets. (MayaJacob et.al. 2004)
There are different types of seal used in machine application and its effectiveness depends on the
material used for manufacturing of seal. PTFE seal: (Polytetrafluoroethylene seal), it is the
synthetic fluoropolymer which have considerable applications. It is also known for sub-name as
Teflon. The PTFE can be formed into a different shape as per the application of coating for
different mechanical parts.
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The following are the mechanical properties of the Teflon seal:
Table.2 Material properties of Teflon
Mechanical
properties
Standards
(ASTM)
Values Unit
Specific gravity D792 2.18 -
Hardness D2240 55-65 Shore hardness
Working
temperature
- -200 to +260 ℃
Thermal
conductivity
D2214 0.22 W/mK
Specific heat at 0 ° 0.96 KJ/Kg-K
Specific heat at 50
°
1.10 KJ/Kg-K
Elongation D1457 210-400 %
Compressive
strength
D695 400-450 N/mm2
Friction coefficient D3028 0.09
Friction Co-
efficient at
dynamic
D3028 0.06
Dielectric Strength D149 55 kV/mm
Co-efficient of
thermal expansion
from 25 to 100 ℃
E831 0.000016 ℃−1
Application of mechanical seal:
 The seal is widely used in industrial application.
 The seal design contains rotary face with the stationary face of the mechanical
equipment.
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 The mechanical seal has considerable advantages such as long life, low maintenance cost
and highly reliable for rotating and dynamic applications.
 Usually, m seal handles light specific gravity liquids at the considerable low temperature
and that have a high vapor pressure that causes an issue for the attached device.
 The mechanical seal must be suitable for the low temperature operating device, it cools
down and running at high speed. There must be sufficient liquid in the area of seal
surfaces.
 Good application of the seal depends on the specific liquid conditions of vapor pressure
and temperature specific gravity.
 The mechanical seal such as AP standard 382 suitable for the overall mechanical
operation.
Rubber:
The rubber contains high molecular weight polymeric substance with viscoelastic properties.
The chemical structure of the rubber is 1, 4-polyisoprene. Isoprene is a diene. The natural rubber
shows all reactions of the unsaturated polymer. The natural rubber reacts with the combination of
sulphur. Which called vulcanization. Rubber material develop plastic and elastic in nature as
raw material. The Vulcanized rubber has a high tensile strength and low material elongation.
Rubber material have good hardness and abrasion resistance high compared to the raw rubber.
There is a variety of combination found in rubber, so it is highly used in manufacturing and
production unit. (P.J.Rae et. al. 2004)
The following are the different types of rubber used in industries
1. Natural rubber or polyisoprene.
2. Styrene-Butadiene-Rubber.
3. Silicone Rubber.
4. Fluorocarbon.
5. Neoprene rubber.
6. Nitrile rubber.
7. VITON.
8. Flurosilicone etc.
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Table.3 Rubber material properties
Properties Values
Specific Gravity 0.90
Thermal conductivity 0.00032 Cal/sec/cm/℃
Dielectric constant 2.45
Dielectric strength 3940 V/mm
Co-efficient of cubic expansion 0.00062 ℃
Heat of combustion 10547.084 cal
l
Power factor 0.15 to 0.2
Refractive index 1.55
Cohesive energy density 6.37 Cal
cc
Volume Resistivity 1015 ohm-cm
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References
D.M.Dattelbaum, P., 2004. The properties of poly(tetrafluoroethylene) (PTFE) in compression. Polymer,
45(22), pp. 7615-7625.
Mahmood M Shokrieh, D. R., 2003. Analysis and optimization of a composite leaf spring. ELSEVIER,
60(3), pp. 317-325.
Maya Jacob, S. T. K., 2004. Mechanical properties of sisal/oil palm hybrid fiber reinforced natural rubber
composites. Composites Science and Technology, 64(7-8), pp. 955-965.
N.K.Anifantis, G. P., 2008. Evaluation of the effective mechanical properties of single walled carbon
nanotubes using a spring based finite element approach. ELSEVIER, 41(4), pp. 561-569.
R.Naik, R. S. T., 2004. Properties of concrete containing scrap-tire rubber – an overview. Waste
Management, 24(6), pp. 563-569.
V.Lewis, C. Y. H. H. S., 2002. Hypotheses that correlate the sequence, structure, and mechanical
properties of spider silk proteins. ELSEVIER, 24(2-3), pp. 271-275.
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