tailieunhanh - Harris' Shock and Vibration Handbook Part 16

Tham khảo tài liệu 'harris' shock and vibration handbook part 16', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | TORSIONAL VIBRATION IN RECIPROCATING AND ROTATING MACHINES If the shaft is solid assume ư. . The factor a2 is a web-thickness modification determined as follows If 4h l is greater than 2Z then a2 - 4h l. If 4h l 2Z assume a2 factor a3 is a modification for web chamfering determined as follows If the webs are chamfered estimate a3 by comparison with the cuts on Fig. FIGURE Schematic diagram of one crank of a crankshaft. Cut AB and A B a3 cut CD alone 3 cut CD and CD a3 cut EF alone a3 cut EF and E F a3 if ends are square a3 . The factor a4 is a modification for bearing support given by Al3 w 4 i 4 B For marine engine and large stationary engine shafts A B For auto and aircraft engine shafts A B If a4 as given by Eq. is less than assume a value of . The Constant s formula Eq. is recommended for shafts with large bores and heavy chamfers. Changes in Section. The shafting of an engine system may contain elements such as changes of section collars shrunk and keyed armatures etc. which require the exercise of judgment in the assessment of stiffness. For a change of section having a fillet radius equal to 10 percent of the smaller diameter the stiffness can be estimated by assuming that the smaller shaft is lengthened and the larger shaft is shortened by a length X obtained from the curve of Fig. . This also may be applied to flanges where D is the bolt diameter. The stiffening effect of collars can be ignored. Shrunk and Keyed Parts. The stiffness of shrunk and keyed parts is difficult to estimate as the stiffening effect depends to a large extent on the tightness of the shrunk fit and keying. The most reliable values of stiffness are obtained by neglecting the stiffening effect of an armature and assuming that the armature acts as a concentrated mass at the center of the shrunk or keyed fit. Some armature spiders and flywheels have considerable .