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Fasteners 2

Fasteners 2. Stiffness of joints Fatigue of preloaded connections. Three Methods. Average cone area (Norton) Integrated cone method (Shigley) Finite element model (Wileman). Cone Frusta Method (text). (14.17 a ). where: d 2 = 1.5 d d 3 = 1.5 d + l m tan φ let φ = 30 °.

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Fasteners 2

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  1. Fasteners 2 Stiffness of joints Fatigue of preloaded connections

  2. Three Methods • Average cone area (Norton) • Integrated cone method (Shigley) • Finite element model (Wileman) MCEN 3025

  3. Cone Frusta Method (text) (14.17a) where: d2 = 1.5 d d3 = 1.5 d + lmtanφ let φ= 30° Replace cones by annular cylinder of effective area, Am MCEN 3025

  4. Integrated Cone Method (Shigley) Where dw = washer diameter MCEN 3025

  5. Finite Element Model (14.17b) MCEN 3025

  6. Stiffness Parameters for FEA Method Table 14-9 Use in equation 14.17b (prev. page) MCEN 3025

  7. Comparison MCEN 3025

  8. Fatigue Loading Most of the applied repeated load goes into relaxing the joint Much less of the applied repeated load is felt by the bolt MCEN 3025

  9. Fatigue Strength (14.15) Alternating stress Mean stress Preload stress Kf = bolt fatigue stress-concentration factor (Table 14-8) Kfmusually = 1.0 for preloaded bolts MCEN 3025

  10. Modified-Goodman Analysis (14.16) Load line (σm, σ a) σ i Sm Preload shifts load line to σi σa Se σm Sut MCEN 3025

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