Presentation on theme: "ME1001-BASIC MECHANICAL ENGINEERING. SYLLABUS UNIT I– MACHINE ELEMENTS– I(5 hours) Springs: Helical and leaf springs – Springs in series and parallel."— Presentation transcript:
SPRINGS A spring is an elastic body, which deflects under load and recover to its original shape upon release of the load. It is also resilient member which stores energy once deflected and releases the same as it recovers to its original shape.
APPLICATIONS OF SPRINGS 1.Applying forces and controlling motions, as found in brakes and clutches. 2.Measuring force, as in the case of spring balance. Ex weighing machine (Analogue). 3.Storing energy, as in the case of clock springs & springs used in toys. 4.Reduce the effect of shock loading, as in the case of vehicle suspension ring. 5.Changing the vibration characteristics of machine mounted on foundation beds.
CLASSIFICATION OF SPRINGS 1.Helical tension and compression spring: The helical springs are made up of a wire coiled in the form of a helix and are primarily intended for compressive or tensile loads. The cross-section of the wire from which the spring is made may be circular, square or rectangular. Helical compression springs have applications to resist applied compression forces
CLASSIFICATION OF SPRINGS The major stresses produced in helical springs are shear stresses due to twisting. The load applied is parallel to or along the axis of the spring.
CLASSIFICATION OF SPRINGS Helical compression spring
CLASSIFICATION OF SPRINGS 2. Helical torsion springs: The principal stress induced are tensile and compressive due to bending. These are similar to the helical tension and compression springs. In these springs, the load is subjected to torsion about its axis.
CLASSIFICATION OF SPRINGS Helical torsion springs
CLASSIFICATION OF SPRINGS 3.Spiral Springs: The principal stress induced are tensile and compressive due to bending. These are made of flat strip, wound in the form of spiral. This is subjected to torsion about its axis.
CLASSIFICATION OF SPRINGS 4. Leaf or laminated Springs : The principal stresses are tensile and compressive de to bending. These are made of flat strips of varying lengths, clamped together. These may be cantilever, semi-elliptic or full elliptic in form.
CLASSIFICATION OF SPRINGS 5. Belleville springs: The principal stress are tensile and compressive de to bending. These are made in the form of coned discs which may be stacked so as to give the required spring load- deflection characteristics.
MATERIALS OF SPRINGS Commonly from alloy steels, High carbon steel (0.7 – 1 % C) or carbon alloy steel. The most common spring steels are music wire, oil tempered wire, silicon, Chrome vanadium. Stainless steel, Spring brass, Phosphor bronze, monel & titanium are used for corrosion resistance spring.
Solid Length :When the compression spring is compressed until the coils come in contact with each other, then the spring is said to be solid. The solid length of a spring is the product of total number of coils and the diameter of the wire. Solid length, L s = n x d Where, n = number of coils Free Length (L o ) : The free length of a compression spring is the length of the spring in the free or unloaded condition. Free length, L o = Solid Length + Maximum Compression deflection + Clearance between adjacent coils (1mm).
TERMINOLOGY IN SPRINGS Spring Index (C): The ratio of mean coil diameter to wire diameter. A low index indicates a tightly wound spring (a relatively large wire size wound around a relatively small diameter mandrel giving a high rate). C=d/D Spring rate(K): The Spring rate is defined as the force required to produce unit deflection of the spring. It can also be said as stiffness or spring constant. K =F/ Where F is the load applied, is the deflection of the spring.
TERMINOLOGY IN SPRINGS Pitch (P) : The distance from center to center of the wire in adjacent active coils. The pitch of the coil is defined as the axial distance between adjacent coils in uncompressed state. P = Free length / (n-1)
SPRING COMBINATIONS Parallel arrangement: In parallel the spring are arranged side by side. The deflection in spring combination is equal to individual spring. K e = K 1 + K 2 +...... + K n
SPRING COMBINATIONS Series Arrangement: When the spring are arranged in series, the total deflection of the spring combination is equal to sum of the deflection of individual springs. 1/ K e = 1/ K 1 + 1/ K 2 +... + 1/ K n
CAM CAM is a device used to convert one simple motion such as rotation to any other motion. A CAM mechanism consist of two moving elements, the cam and the follower which is mounted on the frame.