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Reasons For Damage Of Double Row Ball Slewing Bearing And Improvement
Aug 08, 2017

Reasons for Damage of Double Row Ball Slewing Bearing and Improvement
1 Double Row Ball Slewing Bearing damage phenomenon
In the car cranes, excavators and other types of construction machinery, Double Row Ball Slewing Bearing is to convey the turntable and chassis between the axial load, radial load and tipping moment of the important components.
In the light load conditions, it can work properly, freely rotation. But in the heavy load, especially in the maximum weight and the most significant, the weight of rotation difficult, or even can not turn so that stuck. At this time usually take to reduce the range, adjust the legs or mobile chassis position and other methods to tilt the body to help achieve the rotation of heavy objects to complete the scheduled lifting and other operations. So in the maintenance work will often find Double Row Ball Slewing Bearing raceway has been seriously damaged, both sides of the inner race and the work area in front of the raceway along the raceway in the direction of the ring crack, the seat ring on the raceway force the largest area The occurrence of depression, and in the entire depression area to produce radial cracking.
Discussion on the Cause of Damage of Double Sleeve Rotary Bearing
(1) the impact of safety factors
Double Row Ball Slewing Bearings often operate at low speed and high load conditions, and their carrying capacity is generally expressed in static capacity, rated static capacity as C0 a. The so-called static capacity refers to the track deformation of δ to 3d0 / 10 000 Double Row Ball Slewing Bearing capacity, d0 for the rolling body diameter. The combination of external loads is generally expressed as the equivalent load Cd. Static capacity and equivalent load ratio known as the safety factor, recorded as fs, which is designed and selected Double Row Ball Slewing Bearing the main basis.
When using the method of checking the maximum contact stress between the roller and the raceway, when the Double Row Ball Slewing Bearing is designed, let the allowable thread contact stress [σk line] = 2.0 ~ 2.5 × 102 kN / cm. At present, most manufacturers are based on the size of the external load on the Double Row Ball Slewing Bearing selection calculation. According to the available information, the current small tonnage crane Double Row Ball Slewing Bearing than the large tonnage crane Double Row Ball Slewing Bearing contact stress is small, the actual safety factor is higher. The larger the tonnage of the crane, the greater the diameter of the Double Row Ball Slewing Bearing, the lower the manufacturing accuracy, the safety factor is actually lower, which is the large tonnage crane Double Row Ball Slewing Bearing than the small tonnage crane Double Row Ball Slewing Bearing Easier to damage the root cause. It is generally believed that more than 40 t crane Double Row Ball Slewing Bearings, the line contact stress should not exceed 2.0 × 102 kN / cm, the safety factor should be not less than 1.10.
(2) turntable structural stiffness
Double Row Ball Slewing Bearing is an important part of the various loads between the turntable and the chassis, and its stiffness is not large, mainly depends on the structural rigidity of the chassis and turntable supporting it. In theory, the ideal structure of the turntable for the large stiffness of the cylindrical, so that the turntable can withstand the load evenly distributed, but by the whole height limit can not be done. The results of the finite element analysis of the turntable show that the turntable and the Double Row Ball Slewing Bearing connected to the floor deformation is larger, the greater load conditions are more serious, resulting in the role of the load on a small part of the roller, thus increasing the single The pressure of the roller is very serious. The deformation of the turntable structure changes the contact condition between the roller and the raceway, greatly reducing the contact length and causing a substantial increase in the contact stress. The current widely used contact stress and static capacity of the calculation method, are double pole ball slewing bearing uniform force, and the effective contact length of the roller roller length of 80% of the premise. Obviously, this premise is not consistent with the actual situation. This is another reason that causes the Double Row Ball Slewing Bearing to be easily damaged.