OBJECT: To Determine the Stiffness of the Spring.

APPARATUS:

• Spring
• Vernier Callipers
• Weights

THEORY:

1. Stiffness of Spring
   
2. Hooks Law
   
3. Stiffness
   

METHODOLOGY:

Observation Table:

or

SPRING TEST

AIM: Determine the stiffness of the spring and modulus of rigidity of the spring wire.

OBJECT: To determine the stiffness of the spring and modulus of rigidity of the spring.

APPARATUS:

1. Spring testing machine.
   
2. A spring iii) Vernier caliper,
   
3. Scale.
   
4. Micrometer.
   

DIAGRAM:

THEORY:

Springs are elastic members that distort under load and regain their original shape when the load is removed. They are used in railway carriages, motor cars, scooters, motorcycles, rickshaws, Governors, etc. According to their uses, the springs perform the following Functions:

• 1. To absorb shock or impact loading as in carriage springs.
     
  2. To store energy as in clock springs.
     
  3. To apply forces to and to control motions as in brakes and clutches.
     
  4. To measure forces as in spring balances.
     
  5. To change the variations characteristic of a member as in flexible mounting of motors.
     

The spring is usually made of either high-carbon steel (0.7 to 1.0%) or medium-carbon alloy steel. Phosphor bronze, brass, 18/8 stainless steel Monel, and other metal alloys are used for Corrosion resistance springs. Several types of springs are available for different applications. Springs may be classified as helical springs, leaf springs, and flat springs depending on their shape. They are fabricated of high shear strength materials such as high carbon alloy steel springs form elements of not only mechanical systems but also structural systems. In several cases, it is essential to idealize Complex structural systems with suitable springs.

PROCEDURE:

1. Measure the diameter of the wire of the spring by using the micrometer.
   
2. Measure the diameter of spring coils by using the vernier caliper
   
3. Count the number of turns.
   
4. Insert the spring in the spring testing machine load the spring by a suitable weight and note the corresponding axial deflection in tension or compression.
   
5. Increase the load and take the corresponding axial deflection readings.
   
6. Plot a curve between load and deflection. The shape of the curve gives the stiffness of the Spring.
   

OBSERVATION

Least count of micrometer= ………mm

Diameter of the spring wire, d =……… mm (Mean of three readings) Least count of vernier caliper= ………mm

Diameter of the spring coil, D= ………mm (Mean of three readings) Mean coil diameter, Dm = D – d =……… mm

Number of turns,n =………

TABLE:

Mean k = ……

Modulus of rigidity C = 8𝑊𝐷3𝑛 / 𝛿𝐷4m

Spring Index = 𝐷𝑚 / 𝐷

PRECAUTIONS:

1. The dimension of the spring was measured accurately.
   
2. Deflection obtained in spring was measured accurately.
   

ADVANTAGES:

1. To apply forces and to control motions as in brakes and clutches.
   
2. To store energy as in clock springs.
   
3. This test is conducted to find the material properties of the spring like modulus of rigidity. This can be obtained by observing the values of deflections of the spring with the application of Different amounts of the load along the axis of the spring. The observed values of deflections are compared with the theoretical value for the deflection of the spring under the load and shear modulus is to be obtained.
   
4. To reduce the effect of shock or impact loading as in carriage springs
   

RESULT:

The value of spring constant k of closely coiled helical spring is found to be_____N/ mm

VIVA QUESTIONS:

1. What is meant by stiffness?
2. Define deflection.
3. What are the different types of springs?
4. Define helical spring.
5. What is the strain energy stored in the springs?

APPLICATIONS:

1. To apply forces and control motion, as in brakes and clutches.
   

1. Used in the suspension system.