The noise sources are common mechanical equipment? - bearing knowledge

by:Waxing     2020-06-02
On the issue of the mechanical equipment noise, imbalance is due to the mechanical equipment operation, mechanical shaft concentricity deviation, the dimensional deviation between components or surface defects and the alternating mechanical force generated by the mutual collision and friction equipment sheet metal, bearings, gears and other moving parts vibration and radiation noise source called machinery noise. Here we illustrate one by one to explain all kinds of mechanical equipment noise. Friction noise objects in certain contact with each other under the action of movement, the friction between the object and the friction to reverse direction on the contact surface on the moving object, thus stimulates the object vibration and noise generation. Such as the voice of the underground train braking. Friction noise is mainly caused by friction in the relaxation of the object vibration excited by the noise, when the vibration frequency and natural vibration frequency of the phase object at the same time, to achieve maximum friction noise. The impact noise because of the action of impact mechanical causes strong impact noise. Such as forging hammer is working the mechanical energy can be divided into four parts, the first part of work, the second part is converted into heat energy, the third part, through the base in the form of a solid sound spread to all around the ground, the fourth part is converted to make the parts can produce the vibration of elastic deformation. Part part of the elastic deformation vibration can again in the form of sound waves to space radiation, formed the impact noise, the noise can also be broken down into jet noise generated at the moment of impact, pressure pulse noise and structure noise. With the impact of structural noise is the largest, longest radiated noise. Impact noise has the following characteristics: when a collision occurs between a hard smooth object, short duration, force is big, the incentive of wide frequency band, mode of vibration excitation object itself is much, the wide-band noise impact; If collision happened between the soft matte object, the action time is relatively long, small forces, incentive of the narrow frequency band, excitation mode of vibration. Structure mechanical equipment noise is forced vibration due to mechanical vibration system and natural vibration caused by together, one of the natural vibration played a leading role, natural vibration frequency is the main component of the noise, the natural vibration frequency of vibration system depends on the structure of the system characteristics and parameters, the so called this kind of noise is the structure noise. Any mechanical parts has its inherent vibration mode, different mode of vibration corresponds to different vibration frequency. The mode of vibration, frequency, and the structure of the parts, the physical properties of the material or parts shape and boundary conditions of vibration. Material of the modulus of elasticity is larger, the more material thick, thick, its inherent frequency is high; Material area is larger, that is, the more long, the greater the plate area, its inherent frequency is low. Gear meshing of gear noise or gears, because of a collision or friction may arouse the vibration of the gear body, this case is called gear noise radiation. Excitation noise usually produced by periodic force of rotating machinery. The most simple periodic force is by the axis of rotation, the flywheel rotation system such as static and dynamic imbalance caused by the eccentric force. The quality of this force is proportional to the rotation system and static and dynamic synthesis eccentricity, also will be proportional to the square rotation velocity. When the speed of the rotation system reaches the critical speed, the system itself will produce great vibration, and vibration power passed to the connected with other mechanical parts, aroused the strong noise. Stimulate the noise as part the existence of the gap, the structure rigidity is not enough or severe friction increases. Bearing noise bearing inner relative motion between the parts of the friction and vibration, or rotational part imbalance ( Reflected in the shaft under the condition of different heart) , relative motion between the parts of impact, etc. , will result in bearing noise.
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