Question

Design an infinite-life helical coil extension spring with full end loops and generous loop-bend radii for a minimum load of 9 lbf and a maximum load of 18 lbf, with an accompanying stretch of in. The spring is for food-service equipment and must be stainless steel. The outside diameter of the coil cannot exceed 1 in, and the free length cannot exceed 21 in. Using a fatigue design factor of nf 2, complete the design. Use the Gerber criterion with Table 10-8 Table 10-8 Maximum Allowable Stresses for ASTM A228 and Type 302 Stainless Steel Helical Extension Springs in Cyclic Applications Source: From Design Handbook, 1987, p. 52. Courtesy of Associated Spring Percent of Tensile Strength In Torsion Number of Cycles 105 In Bending End 51 47 45 Body End 36 34 30 28 107 30 This information is based on the following conditions: not shot-peened, no surg Stress ratio 0 ing and ambient environment with a low temperature heat treatment applied.

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