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This material was developed for the IPA by O’Donnell & Associates,
Inc.
The use of perforated materials is limited by the lack of reliable strength
and stiffness properties for use in design. The following information covers
the strength of materials perforated with round holes in a standard staggered
60° pattern as shown in Figure (1).
Round holes arranged in a standard 60° triangular pattern ranging from
.20” to ¾” account for more than half of the perforating
industry’s production. They produce the strongest pattern and are
the most versatile in their application. The standard 60° staggered
formation is the most popular hole arrangement because of its inherent
strength and the wide range of open areas it provides. In perforating this
pattern, the direction of the stagger is the short dimension or width of
the sheet as illustrated. The straight row of closely spaced holes is parallel
to the long dimension or length of the sheet. This is the so-called “closed
pattern.” Under special order, the holes may be punched in the “open
pattern.” The directional properties are then reversed from those
described herein. Refer to Figure (1) for the length and width directions
corresponding to the directional results given in the Tables.
Equivalent Solid Material Concept.
The concept of equivalent solid material is widely used for design analyses
of perforated materials. As applied herein, the equivalent strength of
the perforated material is used in place of the strength of the solid material.
By evaluating the effect of the perforations on the yield strength of the
material, the equivalent yield strength of the perforated material, (S*),
can be obtained as a function of the yield strength of the solid or unperforated
material, S. Thus, the designer is able to determine safety margins for
the perforated material for any geometry of application and any loading
conditions. The S*/S ratios are the same for bending and stretching of
the material. Have the S*/S ratios for the particular penetration pattern
of interest, it is therefore easy for the designer to determine what thickness
of perforated material will provide strength equal to that of the unperforated
material.
Perforated material has different strengths depending on the direction
of loading. Values of S*/S are given for the width (strongest) and the
length (weakest) directions. The values for the length direction have been
calculated conservatively.
Click on a link below.
Strength of perforated metal.
Elastic properties of perforated
metal.
How perforated metals are used in
acoustics.
EMI shielding effectiveness
of perforated metals.
Pressure loss through perforated
plate (air).
Pressure loss through perforated
plate (fluid).
Flatness tolerances.
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