### Interview Questions (Design of Machine Elements - Springs)

What are the end conditions of spring?

• Plain end.
• Plain and ground end
• Squared end
• Squared and ground end.

What is buckling of springs?
The helical compression spring behaves like a column and buckles at a comparatively small load when the length of the spring is more than 4 times the mean coil diameter.

What is a surge in springs?
The material is subjected to higher stresses, which may cause early fatigue failure. This effect is called a spring surge.

What is a laminated leaf spring?
In order to increase, the load-carrying capacity, the number of flat plates are placed and below the other.

What are semi-elliptical leaf springs?
The spring consists of a number of leaves, which are held together by U-clips. The longleaf fastened to the supported is called master leaf. Remaining leaves are called as graduated leaves.

What is nipping of laminated leaf spring?
Pre-stressing of leaf springs is obtained by a difference of radii of curvature known as nipping.

What are the various applications of springs?
The springs are used in various applications, they are

• Used to absorb energy or shocks (e.g. shock absorbers, buffers, etc.)
• To apply forces as in brakes clutches, spring-loaded valves, etc.
• To measure forces as in spring balances and engine indicators
• To store energy as in watches

Define free length.
Free length of the spring is the length of the spring when it is a free or unloaded condition. It is equal to the solid length plus the maximum deflection or compression plus clash allowance.
Lf  = solid length + Ymax + 0.15 Ymax

Define the spring index.
Spring index (C) is defined as the ratio of the mean diameter of the coil to the diameter of the wire.
C = D/d

Define the spring rate (stiffness).
The spring stiffness or spring constant is defined as the load required per unit deflection of the spring.
K = W/y
Where, W - Load, y - Deflection

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