**TEST ON TENSION SPRING**

**Aim:**

To determine the modulus of rigidity and stiffness of the given tension spring specimen.

**Apparatus and specimen required:**

1. Spring test machine

2. Tension spring specimen

3. Vernier caliper

**Procedure:**

1. Measure the outer diameter (D) and diameter of the spring coil (D) for the given tension spring.

2. Count the number of turns i.e. coils (n) of the given specimen.

3. Fit the specimen in the top of the hook of the spring testing machince.

4. Adjust the wheel at the top of the machine so that the other end of the specimen can be fitted to the bottom hook in the machine.

5. Note down the initial reading from the scale in the machine.

6. Apply a load of 25kg and note down the scale reading. Increase the load at the rate of 25kg up to a maximum of 100kg and note down the corresponding scale readings.

7. Find the actual deflection of the spring for each load by deducting the initial scale reading from the corresponding scale reading.

8. Calculate the modulus of rigidity for each load applied by using the following formula:

Modulus of rigidity, N = 64PR

^{3}n d

^{4}δWhere, P = Load in N

R = Mean radius of the spring in mm (D –d /2)

d = Diameter of the spring coil in mm

δ = Deflection of the spring in mm

D = Outer diameter of the spring in mm.

9. Determine the stiffness for each load applied by using the following formula:

Stiffness, K = P/δ

10. Find the values of modulus of rigidity and spring constant of the given spring by taking average values.

**Result:**

The modulus of rigidity of the given spring = -------------------N/mm

^{2}The stiffness of the given spring = -------------------N/mm

^{2}**Observation:**

1. Material of the spring specimen =

2. Outer diameter of the spring. D = mm

3. Diameter of the spring coil, d = mm

4. Number of coils / turns, n = Nos.

5. Initial scale reading = cm = mm

Sl.No. | Applied Load in | Scale reading in | Actual deflection in mm | Modulus of rigidity inN/mm^{2} | Stiffness in N/mm | ||

kg | N | cm | mm | ||||

| | | | | | | |

Average | |

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