Spring Note

1. KATHMANDU UNIVERSITY
SCHOOL OF ENGINEERING
DEPARTMENT OF MECHANICAL ENGINEERING
Presented By:
Sandip Paudel [31161]
ME-II (Hydro)
Special Thanks To:
Dr. Ranjit Shrestha sir
Presentation on: Mechanical Springs
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2. Table of Contents
1. Introduction
2. Application of Spring
3. Types of Spring
4. Spring Materials
5. Terminologies Used in Helical Spring
6. References
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3. Acknowledgment
The information on this slide was obtained mainly from the books Design Elements (V.B. Bhandari),
Machine Design (R.S. Khurmi), and Fundamentals of Machine Elements (B. J. H. S. R. S. Bo O.
Jacobson)There are no copyrights intended, and the main objective is education.
All the figures/illustration used in the slides are taken from different website, books and research papers
and is properly cited with references at the end.
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4. Introduction
• Mechanical springs are flexible/elastic machine element
• It stores mechanical potential energy when deformed by compression,
extension or torsion [1]
• Changes shape when a force is applied to it and returns to its original
shape when the force is removed
• The absorbed energy is retained in the spring and is restored if the
spring returns to its original shape
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Application of spring as a
shock absorber

5. Application of Spring
• Springs are used to absorb vibration and shock.
• Used to store energy and are found in clocks, toys, video
cameras, circuit breakers, and starters
• Springs, such as those used in weighing balances and scales, are
used to measure force.
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Clock Spring (Torsion) [2]
Spring Scale [3]

6. Types of Spring
Types of spring according to motion are:
• Linear Spring: Linear springs are designed to deal with in-line motion (to and
fro).
o When a force is applied in the direction of the spring's length, it deforms and
stores energy in the form of potential energy
o Many variables affect storage capacity, including spring diameter, wire
diameter utilized in spring, spring elasticity, and so on
o Used for a quick release of energy such as in shock absorber
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Linear Spring[4]

7. Types of Spring
Types of spring according to motion are:
• Torsional Spring: Torsional springs are used to deal with rotational
motions
• Used for slow release of stored energy
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Torsional spring used in toy
car [5]

8. Types of Spring
Types of spring according to shape are:
❖ Helical or Coil Spring: Helical springs are formed of coiled wire in
the shape of a helix and are designed primarily for compressive or
tensile loads
• The helical spring is produced from a wire with a circular cross-
section that has been bent into the shape of a helix
• Helical spring is further classified as Tension (Closely coiled) helical
spring and Compression (Open coiled) helical spring
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Torsional spring used in toy
car[5]

9. Types of Spring
Types of Helical spring are:
• Tension or closely coiled spring: Spring wire is coiled so close that the
plane containing each coil is almost at the right angle to the axis of helix
• Helix angle is less than 10 degrees
• Spring shortens when external force acts along the axis of the spring
• Though spring is compressed, wire of the spring is subjected to torsional
shear stress
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Compression spring (a) &
Extension spring (b) [6]

10. Types of Spring
Types of Helical spring are:
• Compression or open coiled spring: Spring wire is coiled with large
gap between adjacent coils
• Helix angle is more than 10 degrees
• Spring elongates when external force acts along the axis of the spring
• Though spring is elongated, wire of the spring is subjected to
torsional shear stress
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Compression spring (a) &
Extension spring (b) [6]

11. Types of Spring
Types of spring according to shape are:
❖Conical and Volute Spring: Type of compression spring with
conical shape
• Conical springs are wounded with uniform pitch
• Volute springs are wounded in the form of paraboloids with
constant pitch angle and lead angles
• Spring can be partially or entirely collapsible
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Conical and Volute Spring [7]

12. Types of Spring
Types of spring according to shape are:
❖Torsion Spring: They can be either helical or spiral type
• Construction is similar to compression or extension spring
• Difference is that ends of the spring is designed to load a
torque about the axis of coil
• Though spring is subjected to torsional moment, the wire is
subjected to bending stress since wire resists bending moment
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Compression spring (a) &
Extension spring (b) [8]

13. Types of Spring
Types of spring according to shape are:
❖ Laminated or Leaf Spring: Series of flat plates usually of semi-
elliptical shape
• Flat plate are called leafs
• Leaves are held together by means of U-bolts and a center clip
• Longest leaf at the top is called master leaf
• Length of leaves gradually decreases from top leaf to bottom leaf
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Illustration of a leaf spring
used in an automotive
application [9]

14. Types of Spring
Types of spring according to shape are:
❖ Laminated or Leaf Spring: Series of flat plates usually of semi-
elliptical shape
• Multi leaf spring are provided with one or two extra leaves in
addition to master leaf to support transverse shear force
• It can carry lateral load, withstand the shocks provided by the
vehicles
• Different forms of leaf spring are available on the market
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Illustration of a leaf spring
used in an automotive
application [9]

15. Types of Spring
Types of spring according to shape are:
❖ Disc or Belleville Spring: Coned disk shaped spring with hole in the
center
• Beneficial when significant forces are required for modest spring
deflections
• It can carry lateral load, withstand the shocks provided by the vehicles
• Is used in plate clutches and brakes, relief valves, and a wide range of
fastened connections
• Equally distributes the load instead of just concentrating on one part of
the washer
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Different form of Belleville
Spring [10]

16. Types of Spring
Types of spring according to shape are:
❖ Disc or Belleville Spring: Can be stacked in series, parallel, or
series-parallel configurations
• These combinations allow a variety of spring constants
• Is used in plate clutches and brakes, relief valves, and a wide range
of When two Belleville springs are connected in series, they
provide twofold deflection for the same force
• When two Belleville springs are connected in parallel, the force for
a given deflection is nearly doubled.
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Belleville spring combination
[11]

17. Spring Materials
Spring's material should have a high fatigue strength, ductility, resilience, and creep resistance
Selection of materials depends on: load acting on the spring
• The stress range across which the spring operates
• Estimated fatigue life
• Environmental conditions in which the spring will function in terms of temperature and corrosive
atmosphere
• Degree of distortion encountered while manufacturing the spring
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18. Spring Materials
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Common spring materials properties
[9]

19. Terminologies Used in Helical Spring
The dimensions of Helical spring subjected to compressive force is given
below:
d = wire diameter of spring (mm)
Di= inside diameter of spring coil (mm)
Do= outside diameter of spring coil (mm)
D = mean coil diameter (mm)
Therefore, D= (Di+Do)/2
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Terminologies of Helical
Spring [6]

20. Terminologies Used in Helical Spring
❖Spring Index: Defined as the mean coil diameter divided by the
wire diameter
C= D/d
• C will determine the strength of spring
• If (C<3), more stress in wire due to curvature effect, difficult to
manufacture, more possibility of cracking
• If (C>15), large variation in coil diameter, prone to buckling, easily
tangles
• In practical applications, the spring index usually varies from 4 to 12
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Terminologies of Helical
Spring [6]

21. Terminologies Used in Helical Spring
❖Curvature Effect:
• When wire diameter is close to coil diameter, inside length of spring
segment is significantly shorter than outside length
• Shearing strain is greater in the inner segment than in the outer
segment for a given magnitude of torsion
• This unequal shearing strain is called Curvature effect
• Curvature effect reduces as spring index increases
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Curvature effect [12]

22. Terminologies Used in Helical Spring
❖Curvature Effect:
• When wire diameter is close to coil diameter, inside length of spring
segment is significantly shorter than outside length
• Shearing strain is greater in the inner segment than in the outer
segment for a given magnitude of torsion
• This unequal shearing strain is called Curvature effect
• Curvature effect reduces as spring index increases
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Curvature effect [12]

23. Terminologies Used in Helical Spring
❖Curvature Effect:
• Higher the spring index (C= D/d), the lower the curvature effect
• This effect can be seen in Railway carriage suspensions, wire
diameter is large in comparison to coil diameter, making curvature
effect strong
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Curvature effect [12]

24. Terminologies Used in Helical Spring
❖ Spring Rate: The spring rate is the amount of weight required to compress a spring one inch
• Spring rate, k = W / δ
• where, W = Load, and
• δ = Deflection of the spring
• . If the spring's rate is linear, the weight on the spring has no effect on its rate
• 200 kg load applied to spring, compress by one inch
• Another 200 kg compresses another inch
• While, 400 kg load is applied, still spring rate remains 200 kg per inch
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25. Terminologies Used in Helical Spring
❖Free Length: Free length is defined as the axial length of an unloaded helical compression spring
• In this situation, no external force acts on the spring.
Free length = compressed length + δ= solid length + total axial gap + δ
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Spring length terminology [6]

26. Terminologies Used in Helical Spring
❖Solid Length: : Solid length is defined as the axial length of the spring which is so compressed that
the adjacent coils touch each other
• The spring is totally compressed in this situation, and additional compression is not possible
Solid length=Nt*d
Where, Nt=Total number of coils
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27. Terminologies Used in Helical Spring
❖Compressed Length: The axial length of the spring when subjected to maximal compressive force is
defined as compressed length
• When the spring is fully loaded, there should be some gap or clearance between the adjacent coils
• The space is necessary to prevent the coils from colliding
• Total axial gap = (Nt – 1) *Gap between adjacent coils
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28. Terminologies Used in Helical Spring
❖Pitch: The pitch of the coil is defined as the axial distance between neighboring coils in the spring's
uncompressed state
P=(Free length)/(Nt – 1)
❖Spring Stiffness: The spring stiffness (k) is defined as the force required to produce unit deflection.
K=P/δ
where, K = stiffness of the spring (N/mm),P = axial spring force (N)
d = axial deflection of the spring corresponding to the force P (mm)
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29. References
• [1] Engineering Product Design, "Mechanical Springs," [Online]. Available:
https://engineeringproductdesign.com/knowledge-base/springs/. [Accessed 24 11 2022].
• [2] A. Oblak, "Clock Spring," [Online]. Available: https://grabcad.com/library/clock-spring-1. [Accessed 1 12
2022].
• [3] Educalingo, "Spring Scale," [Online]. Available: https://educalingo.com/en/dic-en/spring-scale.
• [4] Efunda- Engineering Fundamentals, "Spring calculator," [Online]. Available:
https://www.efunda.com/designstandards/springs/calc_comp_force.cfm.
• [5] Ebay, "10 x Clockwork motors with keys," [Online]. Available: https://www.ebay.com/itm/221389562412.
[Accessed 1 12 2022].
• [6] V. B. Bhandari, "Springs," in Design of Machine Elements, pp. 393-444.
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30. References
• [7] J. G. R.S. KHURMI, "Springs," in Machine Design, pp. 820-884.
• [8] ECPlaza, "ECPlaza," [Online]. Available: https://www.ecplaza.net/offers/mouse-trap-spring-and-
catch_9078930. [Accessed 1 12 2022].
• [9] B. J. H. S. R. S. Bo O. Jacobson, "Springs," in Fundamentals of Machine Elements, pp. 492-512.
• [10] Smelease, "Type of spring and their application," [Online]. Available:
https://www.smlease.com/entries/mechanism/types-of-springs-and-their-applications/.
• [11] S. Thorat, "Springs – Types, Diagram, Design, Material, Advantages, Application," [Online].
Available: https://learnmech.com/types-of-mechanical-springs-advantages/. [Accessed 1 12 2022].
• [12] [Online]. Available: http://icet.ac.in/Uploads/Downloads/2_MODULE%205.pdf.
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31. Thank You!
Any suggestions and queries are highly appreciated.
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