ABMA 9:2015 pdf download

ABMA 9:2015 pdf download.Load Ratings And Fatigue Life For Ball Bearings ANSI/ABMA 9:2015
1.2 Life Criterion
Even if ball bearings are properly mounted, adequately lubricated, protected from foreign matter, and are not subjected to extreme operating conditions, they can ultimately fatigue. Under ideal conditions, the repeated stresses developed in the contact areas between the ball and the raceways eventually can result in fatigue of the material which manifests itself as spalling of the load carrying surfaces. In most applications the fatigue life is the maximum useful life of a bearing. This fatigue is the criterion of life used as the basis for the first part of this standard. Fatigue life calculated in accordance with this standard does not represent the maximum that can be attained by applying all known technology to ball bearing design and application. Neither does it represent the minimum that should be expected of a bearing made by a producer lacking skill and experience in the design and manufacture of ball bearings, even though the bearing meets the geometric parameters given below. The calculated fatigue life represents the performance normally expected from high quality bearings made by reputable manufacturers. Manufacturers can supply longer lived bearings by the application of advanced materials and manufacturing processes. The present standard has evolved as a means for bearing users to specify a reasonable standard of performance for the bearing they wish to purchase.
1.3 Static Load Criterion
A static load is a load acting on a non-rotating bearing. Permanent deformations appear in balls and raceways under a static load of moderate magnitude and increase gradually with increasing load. It is often impractical to establish whether the deformations appearing in a bearing in a specific application are permissible by testing the bearing in that application. Other methods are therefore required to establish the suitability of the bearing selected.Experience shows that a total permanent deformation of 0.0001 of the rolling element diameter, at the center of the most heavily loaded ball/raceway contact, can be tolerated in most bearing applications without the subsequent bearing operation being impaired. The basic static load rating is, therefore, given a magnitude such that approximately this deformation occurs when the static equivalent load is equal to the load rating. Tests indicate that a load of the magnitude in question may be considered to correspond to a calculated contact stress of; 4,600 MPa (667,000 psi) for self-aligning ball bearings, and 4,200 MPa (609,000 psi) for all other ball bearings at the center of the most heavily loaded rolling element/raceway contact. The formulae and factors for the calculation of the basic static load ratings are based on these contact stresses. The permissible static equivalent load may be smaller than, equal to or greater than the basic static load rating, depending on the requirements for smoothness of operation and friction, as well as on actual contact surface geometry. Bearing users without previous experience of these conditions should consult the bearing manufacturers.
3. DEFINITIONS
For the purposes of this Standard, the definitions given in ANSI/ABMA/ISO Standard 5593 together with the following apply. 3.1 Life For an individual rolling bearing, the number of revolutions which one of the bearing rings (or washers) makes in relation to the other ring (or washer) before the first evidence of fatigue develops in the material of one of the rings (or washers) or one of the rolling elements. NOTE: Life may also be expressed in number of hours of operation at a given constant speed of rotation. 3.2 Reliability (in the context of bearing life) For a group of apparently identical rolling bearings, operating under the same conditions, the percentage of the group that is expected to attain or exceed a specified life. NOTE: The reliability of an individual rolling bearing is the probability that the bearing will attain or exceed a specified life.