Study On Ablative Failure Mechanism And Running-in Process Improvement Of Brush-Slip Ring

As a key sliding electrical contact component in radar equipment,brush and slip ring can realize stable transmission of electric energy and signal between rotating part and fixed part.Its reliability is one of the important factors restricting the stable operation of radar.In order to reduce the brush-slip ring contact resistance,the brush is carried out a running-in process to form a curved contact between the brush and slip ring before being put into use.After a unit extended the running-in time of the brush from 2 hours to 60 hours,the ablative phenomenon of the contact area occurred several times within a year after the brush was put into use.The key to solve the problem is to explore the thermal failure mechanism of brush-slip ring based on the detection and analysis of the thermal failure phenomenon after the extension of brush-slip ring running-in time,and to put forward specific improvement measures for the running-in process,so as to reduce the risk of thermal failure of brush-slip ring and extend the service life.Aiming at the ablative fault of the brush-slip ring system in a certain type of radar,this paper establishes the fault tree through the analysis and detection of the ablative phenomenon of the fault samples,analyzes the initial origin of the thermal failure combined with thermal simulation modeling,and proposes a targeted improvement scheme for the existing running-in process.Then,through the running-in experiment simulation,tribology and electrical contact theory,this paper analyzes the sliding wear and electrical contact characteristics during the running-in process of the brushes,compares and studies the effect of the improved running-in process on brush wear,brush-slip ring contact area,and running-in efficiency.Finally,the sliding electrical contact characteristics of the brush in the use stage were studied by simulation experiments,and the sliding contact resistance degradation trend prediction model was established to predict the overall change trend of the brush-slip ring contact resistance under the two processes,and evaluate the degree of reliability improvement of the improved running-in process for the brush-slip ring.Based on the fault sample detection,fault tree analysis and transient thermal simulation,it is shown that when the real contact area of brush and slip ring is low,the temperature of the contact can reach the melting point of brush material and lead to welding after short-term loading of large transient current,which is the cause of thermal failure of brush slip ring.In order to reduce the risk of contact welding,this paper proposes an improved running scheme that increases the actual contact area between brush and slip ring,reduces contact resistance and improves running-in efficiency,that is,increases the elastic coefficient of brush pressing spring by 4 times and shorens the running-in time by 1/3.By comparing the brush wear volume,wear depth,wear area,surface roughness and sliding contact resistance in the running-in process before and after the improvement,it shows that the new process makes the brush contact interface wear area increase by 2 times,and the brush and slip ring fit better.It is also suggested that the cleaning procedure of wear debris on the contact interface should be increased before the brush is put into use.When the brush is put into use,the contact interface is smoother and the wedge is less,the sliding contact resistance increases slowly,and the sliding electric connection process is more stable.By establishing the brush-slip ring sliding contact resistance degradation model,the particle filter method is used to predict the contact resistance degradation trend.The prediction results show that the service life of the improved running-in process of brush-slip ring is 159%longer than that of the original running process,which proves that the improved running-in process delays the rise of contact resistance and improves the service life of the brush.It can effectively reduce the risk of thermal failure of brush-slip ring.