A spring is an elastic object that stores mechanical energy. The spring is usually made of spring steel. There are many spring designs. In everyday use, the term is usually referred to as a spring. With its elasticity, it can control the movement of the machine, mitigate shock or vibration, save energy, measure the force and so on. Widely used in machines and meters.
When a conventional spring has no stiffness change characteristic, when it is compressed or stretched from its rest position, it exerts an opposing force proportional to its length change (this approximately decomposes into a larger deflection). The "rate" or "spring constant" of a spring is the change in the force it exerts, divided by the deflection of the spring. That is, it is the gradient of the force and deflection curves. The rate at which the spring is extended or compressed is expressed in units of force divided by distance. A torsion spring that twists when it is twisted about its axis by an angle that produces a torque proportional to the angle. The rate at which the spring is twisted is divided by the torque in degrees, such as Newton meters per radians or pounds per mile. The reciprocal of the spring rate is compliance, ie if the spring has a velocity of 10 N/mm, its elasticity is 0.1 mm/N. The stiffness (or rate) of the parallel springs is additive, as is the compliance of the spring series.
Springs are made of various elastic materials, the most common being spring steel. The small spring can be wound from a pre-hardened blank, while the larger spring is made of annealed steel and hardens after manufacture. Some non-ferrous metals are also used in phosphor bronze and titanium for parts requiring corrosion resistance and beryllium copper for carrying currents (because of its low electrical resistance).