Rivet Design Stress Formula and Calculator

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Rivet Design Stress Formula and Calculator

Strength of Materials
Engineering Applications

There are two common types of rivets, lap-joint and butt-joint. In a lap-joint rivet the plates to be joined overlap each other and are held together by one or more rows of rivets. In the butt-joint, the plates to be joined are in the same plane and are joined together with a cover plate which is riveted to both plates by one or more rows of rivets. Factors to be considered in evaluating a riveted joint for reliability include type of joint, spacing of rivets, type and size of rivets, hole-size and rivet material.

Preview: Rivet Design Stress Calculator

Both lap-joint and butt-joint rivet assemblies are subject to shear, tension, and crushing.

The shearing stress in the rivet will be:
Eq. 1

$$S_s = {P \over A_s}$$

Where:

S_s = Shearing stress, lb/in²
P = Tensile load on the joint, lbs
A_s = Shear area, in²

The controlling tensile stress in the plate occurs near the rivet hole:

Eq. 2

$$S_T = {P \over ( w - d ) t}$$

Where:

S_T = Tensile stress, lb/in²
w = Width of the plate, in
d = Hole diameter, in
t = Plate thickness, in

The crushing stress due to load transfer at the contact between plate and rivet is:

Eq. 3

$$S_c = {P \over t d}$$

Where:

S_c = Crushing stress level at the area of the rivet, lb/in²

The total design will include a sufficient number of rivets to ensure that the failure of any one rivet because of improper installation or damage will not result in immediate failure of the structure.

Rivet Failure Modes

The primary failure modes in a conventional riveted joint assembly are rivet shear and plate cracking due to load bearing in the sheet. In lower stress aluminum structures, failure is more frequent in the plate, the failure mode being tension cracks starting at stress concentrations on hole-surfaces. In higher stress applications, the failure mode may be either shear of the rivets or plate cracking.

Rivets may fail by:

Shearing through a cross section of the rivet
Crushing

Plates may fail by:

Tearing along a single line from center of rivet hole to edge of plate
Shearing along two parallel lines extending from opposite sides of the rivet hole to the edge of the plate
Tearing between adjacent rivets
Tensile failure of the plate
Crushing

Rivet Failure Rate

Riveted structures designed in accordance with manufacturer’s specifications and assembled without additional stress raisers can be expected to have a fatigue failure rate of 0.08 failures per million hours. Both the method of making the hole for the rivet and the presence of a countersink affect the fatigue strength. For example, for singlerow joints, fatigue strength increases with decreasing pitch; for three-row joints, fatigue strength increases with increasing spacing; and for multi-row joints, fatigue strength increases with increasing numbers of rows. In evaluating rivet joint designs for reliability it is important to recognize the fact that slightly out-of-round holes can increase the failure rate by a factor of 10. Assurance of rivet assembly reliability is normally assured by trial and error experimentation on sample products

Reference:

Hindhede, U., et al, “Machine Design Fundamentals”, John Wiley & Sons, NY, 1983
Shigley, J.E., Mischke, C.R., Mechanical Engineering Design, McGraw-Hill Book Co., NY, 1989.010
Reliability Analysis Center, “Nonelectronic Parts Reliability Data”, NPRD-95
Mechanical Engineers Handbook, Myer Kutz, et al, John Wiley & Sons, 1986
Mechanical Designers’ Workbook, “Fastening, Joining & Connecting”, J. Shigley and C. Mischke, McGraw-Hill 1986
John H. Bickford, “An Introduction to the Design and Behavior of Bolted Joints”, Marcel Dekker, Inc., 1990
OREDA Offshore Reliability Data, 5th Edition Det Norske Veritas, N-1363 Hovik, Norway 2009 ISBN 978-82-14-04830-8