Chapter I  Introduction

1.1  The main significance of this research

Machinery fault diagnosis technology has developed to identify scientific machine or running state in nearly 40 years. It is to adapt to the need of the actual engineering and the formation of interdisciplinary comprehensive discipline. What it studies is the machine or the unit running status change in the diagnostic message reflection. It is the technology by the machine run in physical phenomenon (sound, vibration, sound launch, hot phenomenon and so on) embarks infers the machine content breakdown and is one kind of typical reverse engineering. Started from the 1960s, along with the machine consummates, the complication and the automation unceasingly the mechanical fault diagnosis technology has developed, and with the contemporary science's and technology's front science union, has made the amazing progress.

The rolling bearing is one kind of general part in each kind of revolving machinery applies. Rolling element bearing is one of the most widely used general part of rotating machinery,and one of the most easily damaged parts of mechanical equipment. A lot of mechanical failure is relevant to the state of rolling element bearings. It is estimated that about 30 percent of mechanical failure is caused by its fault in the rotating machine with rolling element bearings. It is obvious that the quality of rolling element bearings has a great impact on the working condition of electromechanical systems. Because of wrong design, poor working condition or a jump heavy load, bearing will be damaged and worse during the running time. So at present, the fault diagnosis of rolling element bearings is a research hotspot.

But compares with other spare parts, the rolling bearing has a very major characteristic, this is its life leaves the divergence to be very big. Because in the material, the working accuracy, the heat treatment and the assembly quality and so on various aspects is impossible identical, causes one batch of types, the size same bearing, even if works under the same condition, life is different for each bearing, and difference up dozens of times. As a result of bearing's this characteristic, it has this kind of situation in the actual use: Some bearings have significantly exceeded design life and work is still intact; some bearings have not achieved the design life to present the breakdown. Therefore, if carries on according to the design life to the bearing fixed time services, then has the following situation: On the one hand, the bearing surpasses the design life, but works complete the bearing opens down takes abandonment processing, creates the waste; On the other hand, the bearing has not achieved the design life to present the breakdown to insist fixed time services when dismantles the incoming telegram to be waste, causes the machinery after the bearing presents the breakdown and opens down in this period of time to work the precision to drop, has not presented the breakdown to the maintenance time, causes the entire machinery to present the serious accident. Therefore, to the important use's bearing settled when the service is very unscientific, must carry on the operating mode monitor and the failure diagnosis, changes traditional the regular service is the forecasting service, like this both can maintain equipment's sound condition frequently, and can use bearing's service life fully, thus the extension overhaul time, reduces the overhaul time, reduces the disaster dump to lose. Therefore, rolling bearing's operating mode monitor and the failure diagnosis bring to the domestic and foreign many technical personnel's attention.

1.2  Rolling bearing failure diagnosis method

Rolling bearing's operating mode monitor and the failure diagnosis are through to the rolling bearing information and so on vibration which, noise, temperature, operational parameter, smell, divulging displays under each kind of operating mode monitors and the generalized analysis to its active status, the breakdown type and the breakdown order of severity carry on the quality synthetic evaluation the process, mainly includes the examination experiment technology, the signal processing technology, the pattern recognition technology and the forecast appraisal technology 4 basic strokes, thus realizes the examination and the discovery exceptionally, the diagnosis malfunction and the spot, the analysis breakdown type, proposes the diagnosis plan and the diagnosis conclusion goal.

At present, according to the breakdown monitor and the diagnosis technology mechanism's difference, rolling bearing's failure diagnosis technology mainly includes:

1. Vibration signal monitor diagnosis technology

In each bearing failure diagnosis method, the vibration examination is the most commonly used one method. When the bearing part's active face presents weary flaking, the indentation or the localized corrosion, in the bearing movement will present the periodic signal impulse. This kind of periodic signal may by install the sensor (speed or acceleration) receives on the bearing seat, through to vibrates the signal the analysis to be possible to realize to the roll axis undertakes to transport the row state the monitor and the diagnosis.

2. Noise signal monitor diagnosis technology

This method is judges its breakdown through rolling bearing's in movement process noise. Carries on bearing's failure detection with the noise law, the merit does not need to contact was measured that the bearing may obtain the detection signal; its malpractice is separates the bearing unusual sound signal very difficultly from environment each kind of static. Therefore, the noise laws are very generally few are used. But the success example also has, is installs the microphone on the directive strong parabola sounder, collects sound signal which the bearing sends out, and removes other static with the reverse filter, examines the bearing different sound.

3. Temperature signal monitor diagnosis technology

Through installs in the bearing seat (or box body) place temperature sensor monitor temperature, judges the bearing to work whether normally. The temperature monitoring to the bearing load, the speed and the lubrication situation's change reflection is quite sensitive, particularly the bearing overheated phenomenon which causes to the insufficient lubrication is very sensitive. Therefore, because this kind of situation is quite effective. But, when the bearing presents such as the early pitting, flaking, the slight attrition and so on quite small breakdown, the temperature monitoring basically had not reflected that is only when the breakdown achieves certain order of severity, can monitor with this method. Therefore, the temperature monitoring is not suitable for the pitting, partial flaking and so on so-called partial damage class breakdown.