AGMA 07FTM01-2007 pdf free.Estimation of Lifetime for Plastic Gears.
Strength calculation taking the real tooth form into account
The endurance safety against root failure is highly influenced by an optimized transformation from the involute to the root circle. The manufacturing of a gear with a generating process, even with a well rounded tip of the tool, an optimal rounding often cannot be achieved. With a modification, which of course has to be adapted to the contact behavior with the counter gear, the root strength can be increased significantly. For the strength analysis a reliable algorithm was developed based on literature, hints in standards and comparable calculations by FEA software. With this algorithm the complex effort of a FEA calculation usually can be skipped.
All standardized calculation methods determine the root stress based on a simplified model. According to VOl 2545 (in analogy to DIN 3990), the critical cross section is determined by the tangent on the inside of the root curve which intersects the middle line of the tooth at an angle of 30 degrees. Depending on the root rounding, the position of the real critical cross section might deviate more or less. In a paper by B. Obsieger [81 years ago, an approach was proposed for a significant improvement of the calculation method. Depending on the real tooth form for each point in the root area the tooth form YF and the stress correction V factors are calculated and the point is determined at which the product YFXYS reaches a maximum (see fig. 4). This leads to a much more precise calculation method and can be applied without problems to non-involute tooth forms as well.
Applying the formula for Vs as defined in the DIN or the ISO standard as proposed by Obsieger exceeds the defined limits for the formula. It is valid only for the point of the 30 degrees tangent, should not be used for a graphical method and is only for involute tooth forms. However, comparing V in a graphical method and FEA results showed a very good match, so that in most cases the accuracy of both methods should be the same. In addition, the described method is a “worst-case” method, i.e. the calculated safety factors are by definition always smaller than those calculated by the standard: the one point treated in the standard calculation is included in the list of points to be checked according to Obsieger. In contrast to the standard method different root forms can be compared and the benefit or negatives of a root modification can be evaluated.
Following the approach of Obsieger it is possible to locate the critical cross section of the tooth. As an option, the force can be applied at the tip as in ISO 6336 Method C, or at the point of single tooth contact – method B. The strength analysis according to VDI 2545 can be carried out later with this specific data. In addition, it is possible to visualize the geo- metrical course of the stress in the root area and the course of the maximum stress in the root area during the meshing of the gears (figure 5). AGMA 07FTM01 pdf download.
AGMA 07FTM01-2007 pdf free
Note:
Can you help me share this website on your Facebook or others? Many thanks!