B8913 number TB20 plane in the implementation process of the ups and downs training, flight faculty found aircraft landing taxiing, after takeoff and take off the plane, a shaking of the dramatic happened even more and more severe, causing the plane taxiing difficult. After some ups and downs, flight faculty decisive take measures to exit the flight training. The maintenance personnel findings: former tire bearing due to high temperature and melting bite dead and driving wheel rotation, axles and wheels fork sliding occurred dry friction, the quantity of heat of generation will axles and wheels fork melt part, the enormous deformation, tire components CongLun almost fell off a fork. Because of the faculty decisive flight choices, to avoid a safety accidents. This shows, tire bearing used not only for supporting tire, guide wheel rotation direction, reducing friction in the process of turning, and heirs and between the wheel on various kinds of loads. And, bearing the work performance, service life, the economic indicators and reliability are has a great influence, and even in some cases can also cause the flight safety accidents.
One of the basic structure, bearing and stress analysis
TB plane for iron wheel bearing's Ken (Timken) company produces the cone bearing, it consists of four parts: roll in the way, and rolling way, tapered roll bar and maintains a. Normally, rolled in ways, the ways and rolling rolling stick loads, and maintains a rolling stick to each other even ground is separated, lest collided with each other and friction, and to make each roll bar evenly and take turns to bear equal load. Rolling road, rolling in bars and maintains a known collectively as groove components. Usually it and roll the way is divisible (the groove can be fixed in the breakdown of the wheel hub), make installation bearing is more convenient.
Bearing the low carbon steel, the surface carburized processing, it makes bearing has the suitable hardness, resist fatigue, endure the comprehensive performance of sex. Under normal use, the largest bearing temperature range in 120-150 ℃, the temperature of 175 ℃ can be short, the largest cycle contact stress in 2100 ~ 3100 MPa, and maintain common transatlantic cable finally laid low carbon steel is made.
Because the geometry of the taper roller bearings characteristics and design features, it can bear to the axial and comprehensive load. The tao and roll in the center the bearing Angle, able to bear axial thrust and to the ratio of the thrust, the bigger the rolling stick and the groove of a longer line contact, then the stronger the load bearing ability. The plane was in a different working conditions, the bearing force of the different:
1. The plane was in a stationary, static load bearing main bear. The gravity of the aircraft from the stop-P through the bearing load transfer to the roll bar groove, namely the wheel hub. P can along the axial decomposition for axial force N and perpendicular to the way of rolling force F. As shown in figure, produced by the foreign roll P word pressure far outweigh the P in the wheels of the reality, exerting a lot of pressure of the groove.
2. The plane on the ground glide, the main was also under vertical load. Because the ground is not absolute level off, the plane's fluctuation shakes was more the gravity of the plane.
3. Landing, tire grounding moment first mainly by huge impact load of vertical static, and then on to the acceleration of high speed up with the same speed in the ground plane taxiing. If the plane has landed weight, bearing in the functioning of the state did not bear the impact load is a lot of harm. If the plane take lateral spreads grounding, such as the large wind, tire but also by the large lateral load, by lateral friction wheel, as the inertia effect, the plane has a sideways trend. So in the role in the vertical load bearing and lateral load than inside of the big.
Second, bearing common fault mode
L. rolling contact fatigue
Rolling contact fatigue caused by failure, it is to point to bearing in operation during the alternating stress resulting in contact surface or surface and surface formation in the fatigue crack and cause failure. Crack started to form, its surface damage little or look not to come out, until the final stage of the process, crack and spalling will behave very obvious.
Bearing in the load bearing, rolling body and groove between mutual extruding, in the contact position near the regional deformation and stress, because the surface is small, even load not too big, contact stress may also be quite large. Usually, in the contact stress of rolling bearings in 2000-4000 MPa between. The contact stress of the static load bearing determines the capacity of the bearing capacity of the static bearing mainly between the surfaces pressure stress distribution, especially on the distribution of the shear stress. If the body in the contact surface rolling out, the surface is parallel to the direction of the rolling shear stress by alternating stress will change. In a depth its reach maximum amplitude, says it is the maximum dynamic shear stress. Maximum dynamic shear stress on contact fatigue crack the occurrence and spread of plays the leading role, and the largest dynamic shear stress on contact surface of the plastic deformation plays a main role. When rolling stick through the groove of cylindrical surface, and the influence of the shear stress field surface with graphic form from right to left, shown in figure below.
When rolling stick from the location of a position of 3 rolled to process, the stress field in the position of 2 to reverse, the reverse is the main factor to bearing damage. Because of shear stress from + τ 2 y into-τ 2 y, so its maximum shear stress τ Max biggest absolute value | 2 become τ 2 y |, this value maximum shear stress far school τ Max.
Will the shear stress theory into the rolling bearing, bearing installed in the wheel and inner circle is almost motionless, and outer ring and hub in the same high-speed together angular velocity rotating. Usually, on the shaft load direction are the same, so that the ring on a little bit of the largest stress, on that point from the shear stress τ 0, in each cycle (roller great rolled this point) than other point, so that the earliest fatigue damage. But to turn for outer, bear the maximum shear stress τ 0 point is changed, and the outer circumference of the larger, so it's contact fatigue life than inner circle is long. Instead, for inner circle turn, outer ring fixed rolling bearing, outer ring in a shorter life span than the.
Usually, the following factors is easy to cause fatigue crack originated in "surface" :
(1) corrosion spots, operation scratches, the surface inclusion and surface creasing can cause stress concentration and led to the surface of the rolling contact originated in fatigue, crack;
(2) the bad lubrication. Usually cause smaller surface discontinuity defects. For example spalling;
(3) the oil film thickness can not reach critical form bearing surface area of the damage.
In theory, rolling bearing load in the great groove and get great distribution is uniform



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