Effect of thread shape on screw stress concentration by photoelastic measurements

Journal Article · Tue Nov 01 04:00:00 EST 1994 · Journal of Offshore Mechanics and Arctic Engineering; (United States)

DOI:https://doi.org/10.1115/1.2920156· OSTI ID:6944749

Dragoni, E ^[1]

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1. Univ. of Bologna (Italy). Dept. of Mechanics

The screw stress concentration for six nut-bolt connections embodying three different thread profiles and two nut shapes is measured photoelastically. Buttress (nearly zero flank angle), trapezoidal (15-deg flank angle), and triangular (30-deg flank angle) thread forms are examined in combination with standard and lip-type nuts. The effect of the thread profile on the screw stress concentration appears to be dependent upon the kind of nut considered. If the fastening incorporates a standard nut, the buttress thread is stronger than the triangular one, which, in turn, behaves better than the trapezoidal contour. The improvement is roughly a 20% reduction in the stress concentration factor from the trapezoidal to the buttress thread. In the case of lip nut, conversely, this tendency is somewhat reversed, with the trapezoidal thread performing slightly (but not decidedly) better than the other two shapes. Finally, averaged over all three thread forms, the lip nut exhibits a stress concentration factor which is about 50% lower than that of the standard nut.

• OSTI ID: 6944749
• Journal Information: Journal of Offshore Mechanics and Arctic Engineering; (United States), Journal Name: Journal of Offshore Mechanics and Arctic Engineering; (United States) Vol. 116:4; ISSN 0892-7219; ISSN JMOEEX
• Country of Publication: United States
• Language: English

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THREADED JOINTS