CAUTION NOTICE: AGMA technical publications are subject to constant improvement, ANSI/AGMA D04, Fundamental Rating Factors and Calculation. Credit line should read: “Extracted from ANSI/AGMA. Standard D04 or -D04 Fundamental Rating Factors and Calculation Methods for Involute Spur. Citations should read: See ANSI/AGMA D04, Fundamental Rating Factors and Calculation Methods for Involute Spur and Helical Gear.
The statistical probability of failure can be defined in an application in several ways. Since elastic deflections are load dependent, gear tooth profile modifications can be designed to give a uniform velocity ratio only for one load magnitude. Limits in inches to be based on case depth as follows: However, the reduction in tooth root thickness due to protuberance below the active profile is handled correctly by this method.
Under these resonant conditions, the dynamic gear tooth loads may be very high, and operation near a system resonance is to be avoided. A backup ratio of 2.
The use of the 0. In determining the overload factor, consideration should be given to the fact that many prime movers and driven equipment, individually or in combination, develop momentary peak torques appreciably greater than those determined by the nominal ratings of either the prime mover or the driven equipment. Therefore, for those situations, the standard says to use the allowable bending stress number without adjustment, or one can say that the load reversal factor is 1.
Users of this standard should assure themselves that they are using these symbols and terms in 210-1d04 manner indicated herein. The load reversal factor is discussed in Clause The loading arrangement on the shaft has a weight supported by a bearing system that puts a bending load on the shaft.
The four curves of figure 7 provide representative values 2011-d04 KHma based on the accuracy of gearing and misalignment effects which can be expected for the four classes of gearing shown.
The choice of ZN in the shaded zone is influenced by: According to the Modified Goodman failure theory, bending fatigue failure can be predicted by the equation:. This paper also explores failure theories that help explain the origin of the AGMA load reversal factor and how it can be more effectively predicted based on material selections. Curves may be extrapolated beyond the end points shown in figure A. Transmission error is defined as the departure from uniform relative angular motion of the pair of meshing gears.
Allowable stress numbers for steel gears are established by specific quality control requirements for each material type and grade. It includes tables for some common tooth forms and the analytical method for involute gears with generated root fillets.
AGMA application standards may use other empirical factors that are more closely suited to the particular field of application. Allowable stress numbers in this standard are based on cycles, 99 percent reliability and unidirectional loading. These stress values are also shown graphically in Figure 2 where the alternating stress is the amplitude of the sine wave. At this stage the gears are assumed to be initially parallel with no gap if adjustments are planned to be made or the expected gap is combined with the other factors to be determined.
Furthermore, the method of measuring the case as well as the allowable tolerance in case depth may be a matter of agreement between the customer and the manufacturer. Use upper portion of core hardness band which yields heavier case depths for general design purpose and lower portion for high quality material as defined in Experience, however, suggests stress cycle curves for pitting resistance and bending strength of steel gears as shown in figures 17 and Grinding the tooth surface after heat treatment may reduce the residual compressive stresses.
To use these values, the gearing must be maintained in accurate alignment and adequately lubricated so that its accuracy is maintained under the operating conditions. For gearing requiring maximum performance, especially large sizes, coarse pitches, and high working stresses, detailed studies must be made of application, loading, and manufacturing procedures to determine the desired gradients of hardness, strength, and internal residual stresses throughout the tooth.
This equation is valid for the range 1.
Scuffing criteria are not included in this standard. Undercut exists in an area above the theoretical start of active profile.
New Refinements to the Use of AGMA Load Reversal and Reliability Factors
Field experience and test stand experience can be used to select design parameters and lubricant criteria to meet the application. Equation 36 therefore, can be modified to: Therefore, only an experienced engineer should apply knowledge of S–N curves to gear calculations. At the time of development, the editions were valid.
Figure 12 – Variations in hardening pattern obtainable on gear teeth with flame or induction hardening Through hardened gears specified above HB may vary widely in endurance strength, depending on the transformation characteristics of the steel, heat treating technique used and the size and shape of the part. Where specific experience and satisfactory performance has been demonstrated by successful use of established service factors, values of ZN and YN of 1.
The dynamic factor, Kv, does not apply to resonance. The material property data in Table 3 was taken from Jandeska et al. However, caution must be taken to first normalize 2101-e04 material properties to the same statistical reliability before they are applied to Equation Wear may occur when the oil film that separates the contacting surfaces of mating gear teeth is not adequate see AGMA A Such bar testing usually can be accomplished in a few days of run time.
If the value of hc min from equation 45 is less than the value for normal case depth from figure 15, then 2011-d04 minimum value from figure 15 should be used. In these cases, the design should be checked to make certain that the aggma are not permanently deformed.
The formulas are not valid for applications such as robotics or yaw drives where gears are subjected to small oscillatory motion. Intermediate values are not classified since the effect of deviations from the quality standards cannot be evaluated easily.
The intent of the AGMA strength rating formula is to determine the load which can be transmitted for the design life of the gear drive without causing root fillet cracking. Therefore, a minimum n hardness of 25 HRC is acceptable in such cases.
Some of these are: Slower speed gears, with pitch aga velocities less than 0. A non-linear regression analysis was performed in order to convert the statistical probabilities from Table 1 into the corresponding reliability factor of Table 1 in equation form.
The YJ factor calculation uses the stress correction factors developed by Dolan and Broghamer .
Select the AGMA method to save the user having to do this. The influencing parameters can be categorized into four groups, all of which are normal to the manufacturing process but still cause face misalignments of the mating gear teeth.
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