The use of standard sizes facilitates the selection of bearings, collars, couplings, and other hardware. The closest size commercial shafting is 1-15/16 in. Table 10-4: Values of Shock and Fatigue Factors for Rotating Shafts (from ASME Code) Nature of Loading Table 10-4 gives these factors for rotating shafts. This factor accounts for the severity of the loading during stress reversals caused by the revolution of the shaft. The code also recommends the application of a shock and fatigue factor to the computed torsional moment or bending moment. Table 10-3: Values of Stress Concentration Factor for Screw Threads, K Table 10-2: Values of Stress Concentration Factor for Keyways, K These are applied only if the section being analyzed includes either threads or a keyway. Tables 10-2 and 10-3 give stress concentration factors to be applied to keyways and several screw thread types. Although the code does not mention stress concentration factors further, they must be considered in any design.įigures 10-1 through 10-5 give stress concentration factors to be applied to the design stress for various types of section discontinuities. Table 10-2 should also be consulted prior to making allowance for keyways. It is noted that this is equivalent to a stress concentration factor of 1.33. The code also applies a factor of 0.75 to the calculated design stress if the section being considered includes a keyway. For combined stresses, as discussed in Section 10.4, the shear design stress is used. The smaller of the two computed stresses is to be used. According to this code, the basic design stress shall be: The ''Code of Design of Transmission Shafting, 11 which has been published by the ASME as code B 1 7c, 192 7, gives the basic factors to be used in determining the design stresses, either normal or shear. However, it must be modified to account for various loading anomalies. The design stress is obtained from the yield strength of the material to be used. The value to be used for the design maximum shear stress, f s.max, is discussed in the next section.ġ0.5 Design Stresses and Load Variations for Transmission Shafting Where f s and f are obtained from the relations given in Section 10.3.
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