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Alternative discrimination method for several failed NTN bearings
Source: China Bearing Network Time: 2013-08-06
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2. Wear and failure Wear and tear refers to the failure of the relative sliding between the appearances to cause the wear and tear of the working exterior metal. The continuous wear will lead to the gradual damage of the NTN bearing parts; and the end will lead to bearing dimensional accuracy loss and other related problems. Affect the shape modification; the cooperation gap is increased and the operation appearance is modified; the smoothing agent can be affected or the pollution can reach a certain extent to form a smooth loss of smooth function; thus the bearing loss rotation accuracy can not even operate normally. Wear failure is various types One of the common failure modes of bearings; according to the wear method, it can be generally divided into the most common abrasive wear and adhesive wear.
Abrasive wear refers to the abrasion caused by the extrusion of foreign solid particles or hard foreign matter or metal surface between the outer surface of the bearing operation and the relative movement of the touch surface; often the furrow-like scratches are formed on the outer surface of the bearing work. Hard Particles or foreign matter can come from inside the host or other adjacent parts from the host system are fed into the bearing by the smooth medium. Adhesive wear means that the conflicting surface is unevenly affected by the microscopic bulging or foreign matter of the conflicting surface; the smooth condition deteriorates severely. Time; heat generated due to partial conflict; easy to form part of the conflict surface and conflict micro-welding; when the surface is severe, the surface metal can be partially melted; the force on the touch surface tears part of the conflicting joint from the substrate to increase plastic deformation This cyclical process of adhesive tear adhesion constitutes adhesive wear; in general; fine adhesive wear is called scratch; severe adhesive wear is called bite.
3. Crack failure
The main cause of NTN bearing cracking failure is the two major factors of shortcomings and overload. When the applied load exceeds the data strength limit, the cracking of the part is called overload cracking. The overload is caused by the host's sudden fault or the device is not correct. The micro-crack of the bearing parts is shrinking. Holes, air bubbles, large foreign objects, overheating arrangements and partial burns will also cause cracking in the shortcomings during impact overload or severe oscillation; called fault cracking. It should be pointed out; the bearing is in the process of production; In the process of re-inspection, casting and heat treatment quality control, processing and processing, the above-mentioned shortcomings can be correctly analyzed through the instrument; the control must be strengthened in the future. Generally speaking, the general failure of bearing cracking is mostly overload failure.
4. Clearance change
NTN bearing is in operation; because of the influence of external or intrinsic elements; the original cooperation gap is changed; the precision is reduced; even the formation of "biting death" is called the gap modification failure. The external factors such as excessive interference are excessive; the device is not in place; The large amount of expansion caused by temperature rise, instantaneous overload, etc.; the connotation elements such as residual austenite and residual stress are unstable, which are the primary reasons for the failure of the play change.
NTN bearings exhibit the following shortcomings; they cannot be used continuously; new bearings should be replaced immediately. Details are as follows:
(1) Cracks or notches on any of the inner ring, outer ring, roll body and cage of the bearing;
(2) Cracking on any one of the bearing ferrule and the rolling body;
(3) There are significant jams on the raceway surface, the ribs and the rolling body of the bearing;
(4) The bearing cage is worn significantly; perhaps the rivet is significantly relaxed;
(5) There is rust and injury on the raceway surface of the bearing and the rolling body;
(6) There are severe indentations and marks on the raceway surface of the bearing and the rolling body;
(7) There is significant creep in the inner diameter surface of the inner ring of the bearing or the outer diameter surface of the outer ring;
(8) The discoloration due to heat is significant.
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