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BACKGROUND
Spring is a light metal spiral set up which is connected with some weight at one end, and its other end is attached to a wall. This material shows elastic property, and its length varies with the applied force (either tensile or compressive), and the restoring force produced follow a directly proportional relationship with change in length.1 In other words, during application of drive in a spring to fluctuate its natural position, it applies an equal and opposite force (which is also known as restoring force) to the object, and it is given by the relation: F=-kx. This law is also known as “Hooke’s Law“.
Here, k= spring constant,
And, x= deflection produced in the object.
The spring is composed of either high carbon steel (0.7 to 1.0%), or medium carbon alloy steels. Phosphor bronze, brass, 18/8 stainless steel and Monel and other metal alloys are used for corrosion resistance spring.
Spring constant is defined as the characteristics of a spring which is the ratio of the deflecting force to the displacement it makes, as k= (-F/x). So, a large spring constant means that either the spring material causes a small deflection under high force, or the coil thickness of spring is bigger.
Thus, spring constant resembles the stiffness of spring, and every spring has its natural value of spring constant. The phenomenon behind the spring is Newton’s third law which states that there is an equal and opposite reaction for every action.2 Thus, when pulling force is applied on a spring then a restoring force is applied towards inside.
The main objective of this experiment is to determine the spring constant of a material under tension or compression.
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REQUIREMENTS
Materials: Spring Testing Machine
A Spring
Scale
Slotted Weights
Micrometre
A Fine Pointer
A Hook
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PROCEDURE
First of all, measure the diameter of the Wire and coil of spring by using a micrometre and a vernier calliper respectively. Note down the no. of turns, to find its stiffness. Now, attach the spring with the help of a hook in the spring testing machine, and load the slotted weights to the spring and measure its axial deflection in tension or compression by using a pointer and a scale. Take further readings, by increasing the slotted weights in each step. After this, plot a curve between load and deflection, its shape will give the stiffness of the spring.3
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CONCLUSION
The spring constant of material has been successfully determined. It varies from one material to another and resembles the stiffness of the spring, i.e. higher the spring constant, stiffer would be material.
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REFERENCES
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M. T. W. N. L. L. Howell, “Evaluation of Equivalent Spring Stiffness for Use in a Pseudo-Rigid-Body Model of Large-Deflection Compliant Mechanisms,” Journal of Mechanical Design, vol. 118, no. 1, 1994.
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R.Blickhan, “The spring-mass model for running and hopping,” Journal of Biomechanics, vol. 22, no. 11-12, pp. 1217-1227, 1989.
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N. P. Gurao, “MECHANICAL BEHAVIOUR LABORATORY,” Indian Institute of Technology Kanpur, kanpur, 2014.
