CE1263 STRENGTH OF MATERIALS LAB COMPRESSION TEST ON OPEN COIL HELICAL SPRING Anna university lab manual download - Computer Programming

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## Friday, February 4, 2011

COMPRESSIONTEST ON OPEN COIL HELICAL SPRING

Ex.No:05
Date:

Aim:
To determine the stiffness of spring, modulus of rigidity of the spring wire and maximum strain energy stored.
Equipments Required:
1.      Spring testing machine
2.      A open coil spring
3.      Vernier caliper
Formulae:
1. Deflection (d) = 64 WR3N Sec a [ cos2a / N + 2Sin2a /E]      N/mm2
d2

Where,
R=Mean radius of spring coil = (D-d)  / 2
N= Bynver if tyrbs ub sorubg
a=Helix angle of spring
N=Modulus of rigidity of spring Material
E=Youngs modulus of the spring material

1. Tan a = pitch / 2ПR

1. Pitch = (L-d) / n
Where,
d=Dia of spring wire in mm
L=Length of spring in mm
N=no of turns in spring
1. Stiffness of spring (K)=w / d
Where,
d=Deflection of spring in mm

5. Maximum energy stores = 0.5 x Wmax x dmax
Where,
dmax=Maximum deflection

Procedure:
1.      By using vernier caliper measure the diameter of the wire of the spring and also the diameter of spring coil.
2.      Count the number of turns.
3.      Insert the spring in the spring testing machine and load the spring by a suitable weight and note the corresponding axial deflection in compression.
5.      Plot a curve between load and deflection.  The shape fo the curve gives the stiffness of the spring

Observation:
TO determine the wire diameter, and coil diameter of spring ( each 3 readings)
Least count of vernier=

 Sl.No MainScale Reading (MSR) in mm Vernier scale reading (VSR) VSR x LC in mm Total reading = MSR=(VSRxLC) in mm

Diameter of spring coil (D)=
Diameter of spring wire(d)=
Number of turns in spring