AGMA 930-A05 pdf free.Calculated Bending Load Capacity of Powder Metallurgy (P/M) External Spur Gears.
A safety factor is commonly introduced into design calculations to provide greater protection against possible failure. This protection may be sought because of concern that some elements of the design process may have overstated the strength of the material or may have understated the level of the loading. Sometimes the added protection against failure is based on concern for some extremely severe result of failure.
In selecting a value for safety factor, it is first necessary to recognize that many of these concerns have already been addressed elsewhere in the calculations. As for material strength, there have been a whole series of adjustments, such as the selection of the G -1 values from published data, see clause 4, and the various factors defined in clause 5 Similarly for the level of loading, a number of adjustments have been introduced, as described in clause 9. Based on concerns for material strength and loading, unless these adjustments are judged to be inadequate, the suggested value for the safety factor would be one.
This first selection may be increased after consideration of the possible results of failure of the gear under study. It such failure is likely to be followed by severe economic loss, or even more importantly, by injury to those associated with the failed equipment, then the safety factor should reflect the level of the hazards.
Also to be considered is the level of testing that precedes final acceptance of the design. Because the P/M process is used to produce gears for mass production, there is generally the need and opportunity for extensive testing. This, and the recognition that P/M processes are highly consistent, indicates that high safety factors are rarely necessary.
9.1.2 Overload factor for repeated loads, k0t
This factor allows for two types of repeated overloads. One type is the overload that results from operation of the product beyond its nominal rating. If the calculated load capacity is going to be compared to the load associated with the nominal rating, then this factor should be adjusted to reflect this potential overload. The other type is the overload resulting from externally applied dynamic loads. Anything in the drive train that is not steady in its effect on transmitted torque or speed may introduce dynamic torques. For example, non-steady torques are associated with driving members like internal combustion engines or some types of hydraulic motors. They are also associated with varying drive train loads such as reciprocating pumps or intermittent cutting actions.AGMA 930 pdf free download.