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Research Papers: Design and Analysis

Finite Element Analysis of the Cyclic Stress Amplitude of Threaded Fasteners Using Helical Thread Models

[+] Author and Article Information
Toshimichi Fukuoka

Graduate School of Maritime Sciences,  Kobe University, Fukaeminami 5-1-1, Higashinada, Kobe, Hyogo, 658-0022, Japanfukuoka@maritime.kobe-u.ac.jp

Masataka Nomura

Graduate School of Maritime Sciences,  Kobe University, Fukaeminami 5-1-1, Higashinada, Kobe, Hyogo, 658-0022, Japannomura@maritime.kobe-u.ac.jp

Takashi Fuchikami

 Kobe University, Fukaeminami 5-1-1, Higashinada, Kobe, Hyogo, 658-0022, Japan081w523w@stu.kobe-u.ac.jp

J. Pressure Vessel Technol 133(6), 061201 (Oct 03, 2011) (7 pages) doi:10.1115/1.4004559 History: Received September 10, 2009; Revised May 26, 2011; Published October 03, 2011; Online October 03, 2011

Fatigue failures of bolted joints frequently lead to serious accidents in machines and structures. It is well known that fatigue failure is likely to occur around the first thread root of the bolt adjacent to the nut loaded surface and the run-out of bolt thread. That is because high stress amplitudes are generated there due to alternating external forces. Accordingly, it is significantly important to evaluate the stress amplitudes along the thread root in order to rigorously examine the fatigue failure mechanism of bolted joints. In this study, stress amplitude distributions along the thread helix including the thread run-out are analyzed by three-dimensional finite element analysis. The numerical models of the bolted joints are constructed so as to accurately represent the effect of thread helical geometry, using the modeling scheme proposed in the previous study which analyzed the stress concentrations at the thread root. The analytical objectives are bolted joints with axisymmetric geometry except for the helical-shaped threaded portions that are subjected to axisymmetric external forces. It has been substantiated, based on the stress amplitude distributions along the thread helix, which the fatigue failures are likely to originate from the first bolt thread, as in the case of the maximum stress, and the run-out of threads. It has also been shown that a bolt with reduced diameter is effective for the purpose of lowering the stress amplitude at the first thread root of bolt.

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Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Geometry of modeled bolted joint and its boundary and loading conditions

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Figure 2

Finite element model of bolted joint with accurate helical thread geometry

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Figure 3

Mises stress distributions along bolt thread root

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Figure 4

Distributions of axial stress and stress amplitude along bolt thread root

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Figure 5

Stress amplitudes along bolt thread root before complete separation of plate interface

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Figure 6

Stress amplitudes along bolt thread root after complete separation of plate interface

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Figure 7

Effect of initial bolt stress on stress amplitudes

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Figure 8

Effect of external force on stress amplitudes

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Figure 9

Ratio of stress amplitude at first threat root to mean stress amplitude in engaged threads

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Figure 10

Stress amplitude distributions in radial direction from bolt axis toward thread root

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Figure 11

Stress amplitudes along bolt thread root for bolts with reduced shank diameter

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Figure 12

Axial stress distributions and deformation patterns around engaged threads

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