MAXIMUM ALLOWABLE STRESSES FOR COIL EXTENSION SPRINGS IN STATIC AND FATIGUE APPLICATIONS




Maximum Allowable Stresses (KW corrected) for Helical Extension Springs in Static Applications
Material In Torsion In Bending
Body End End
Patented, cold-drawn or hardened and
tempered carbon and low-alloy steels
45 - 50 % 40 % 75 %
Austenitic stainless steel and nonferrous alloys 35 % 30 % 55 %
Source : From Shigley's Mechanical Engineering Design [Ref 2] page 529 and Standard Handbook of Machine Design [Ref-3] Chapter 24 page 33

This information is based on the following conditions: set not removed and low temperature heat treatment applied. For springs that require high initial tension, use the same percent of tensile strength as for end.


MAXIMUM ALLOWABLE TENSILE STRENGTH FOR ASTM A228 AND TYPE 302 STAINLESS STEEL HELICAL EXTENSION SPRINGS IN CYCLIC APPLICATIONS
Number of Cycles Percent of Tensile Strength (In Bending)
105 51 %
106 47 %
107 45 %
Source : From Shigley's Mechanical Engineering Design [Ref 1] page 532 and Standard Handbook of Machine Design [Ref-3] Chapter 24 page 34

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.



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