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Sổ tay tiêu chuẩn thiết kế máy P29

Tham khảo tài liệu 'sổ tay tiêu chuẩn thiết kế máy p29', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 24.34 STANDARD HANDBOOK OF MACHINE DESIGN TABLE 24.12 Maximum Allowable Stresses for ASTM A228 and Type 302 Stainless-Steel Helical Extension Springs in Cyclic Applications Number of Cycles Percent of Tensile Strength In Torsion In Bending Body End End 105 36 34 51 IO6 33 30 47 107 30 28 45 This information is based on the following conditions not shot-peened no surging and ambient environment with a low temperature heat treatment applied. Stress ratio 0. source Associated Spring Barnes Group Inc. 24.5.8 Tolerances Extension springs do not buckle or require guide pins when they are deflected but they may vibrate laterally if loaded or unloaded suddenly. Clearance should be allowed in these cases to eliminate the potential for noise or premature failure. The load toierances are the same as those given for compression springs. Tolerances for free length and for angular relationship of ends are given in Tables 24.13 and 24.14. 24.6 HELICAL TORSION SPRINGS Helical springs that exert a torque or store rotational energy are known as torsion springs. The most frequently used configuration of a torsion spring is the single-body type Fig. 24.23 . Double-bodied springs known as double-torsion springs are sometimes used where dictated by restrictive torque stress and space requirements. It is often less costly to make a pair of single-torsion springs than a double-torsion type. TABLE 24.13 Commercial Free-Length Tolerances for Helical Extension Springs with Initial Tension Spring Free Length inside hooks nun in. Tolerance nun in. Up to 12.7 0.500 0.51 0.020 Over 12.7 to 25.4 0.500 to 1.00 0.76 0.030 Over 25.4 to 50.8 1.00 to 2.00 1.0 0.040 Over 50.8 to 102 2.00 to 4.00 1.5 0.060 Over 102 to 203 4.00 to 8.00 2.4 0.093 Over 203 to 406 8.00 to 16.0 4.0 0.156 Over 406 to 610 16.0 to 24.0 5.5 0.218 source Associated Spring Barnes Group Inc. SPRINGS 24.35 TABLE 24.14 Tolerances on Angular Relationship of Extension Spring Ends Angular Tolerance per Coil Degrees Index 4 5 6 7 8 9 10