Abstract
Bearing units of lifting machines, products of construction, road, aviation, space and other branches of technology are very important structural elements, since the failure of even one bearing can cause the failure of the entire product. The results of experimental verification of the theoretical model of bearing operation under combined loading conditions are presented. The behavior under load of bearing units in the most general case can be represented by a sequence of five design schemes, expressed in the form of five statically indeterminate beams. The purpose of the experiments was to test this model under real loading conditions. The experiments were based on the analysis of the geometric shape of the curved elastic line, which the shaft of the bearing assembly acquires under load. The experimental results confirmed the validity of the model and showed that the previously generally accepted model of a two-support beam is not implemented. The conclusion is confirmed that in responsible lifting machines, as well as in responsible products of construction, road, aviation, space and other branches of technology, it is impractical to calculate bearings according to the traditional method, since an erroneous value of bearing durability can be obtained, overestimated from 28.37 to 26.663.9 times.
Highlights
Increased requirements for long-term trouble-free operation are imposed on the bearing units of lifting machines, as well as to the units of critical products in the construction, road, aviation, space and other branches of technology, since they must operate in the widest range of external operating conditions – from normal to critical and maximum permissible
The carried out experimental studies have confirmed the main provisions of the theoretical model, which are as follows: a) the traditional design model of a two-support beam is not implemented, when loaded with a combined load of ball radial single-row bearings installed in a spindle; b) under conditions of combined loading with a continuously increasing radial force Fr, a sequential transformation of the three main statically indeterminate design models is realized, starting from the “seal with an additional hinged support” model, through a possible “double-sided seal” model to the final model “two double hinged supports”; c) the functions of the supports, which the bearings perform during the loading process, are not constant and can be modified
In the left bearing, the original seal is converted into a double pivot bearing, and in the right bearing – the original pivot bearing is converted into a seal first, and only into a double pivot bearing; d) the time intervals during which the transformation of the current types of supports into subsequent ones occurs on the left and right, differ significantly from each other
Summary
Increased requirements for long-term trouble-free operation are imposed on the bearing units of lifting machines, as well as to the units of critical products in the construction, road, aviation, space and other branches of technology, since they must operate in the widest range of external operating conditions – from normal to critical and maximum permissible. The traditional, generally accepted design model for calculating and designing bearing units is a two-support beam, i.e. a smooth beam mounted on two hinged supports (Figure 1, a). When this beam deflects under the action of an external radial force Fr directed downward, its free ends rise upward, and the cross-sections located on the supports make a hinge rotation at a certain angle α. In this case, one radial reaction occurs at a time on each support RA and RD
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