Jul 20 2002
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Whenever a perforated metal is used, the potential to offer a required level of elasticity can be a crucial factor. By knowing that a perforated metal is not as rigid as a non-perforated metal, elasticity levels can be determined by comparing both types of metals. This comparison is known as the Equivalent Solid Material Concept.
As such, solid material equivalent tests were conducted in an attempt to provide designers with the information required to allow them to make decisions regarding the elasticity of perforated metals.
During the tests, the elasticity of 26 different perforated metal samples was compared with the corresponding solid metal. Since they are responsible for over half of the production in the perforating industry, the tests were carried out on round hole 60° staggered patterns that range between 0.020″ and ¾″. The tested samples are provided in Table 1.
Table 1. Effective elastic properties for IPA standard perforations
| IPA Number |
Perforations |
Centres |
Holes sq. in |
Open Area |
E*/E |
| 100 |
0.020” |
- |
625 |
20% |
0.565 |
| 106 |
1/16” |
1/8” |
- |
23% |
0.529 |
| 107 |
5/64” |
7/64” |
- |
46% |
0.248 |
| 108 |
5/64” |
1/8” |
- |
36% |
0.362 |
| 109 |
3/32” |
5/32” |
- |
32% |
0.395 |
| 110 |
3/32” |
3/16” |
- |
23% |
0.529 |
| 112 |
1/10” |
5/32” |
- |
36% |
0.342 |
| 113 |
1/8” |
3/16” |
- |
40% |
0.310 |
| 114 |
1/8” |
7/32” |
- |
29% |
0.436 |
| 115 |
1/8” |
¼” |
- |
23% |
0.529 |
| 116 |
5/32” |
7/32” |
- |
46% |
0.249 |
| 117 |
5/32” |
¼” |
- |
36% |
0.362 |
| 118 |
3/16” |
¼” |
- |
51% |
0.205 |
| 119 |
3/16” |
5/16” |
- |
33% |
0.395 |
| 120 |
¼” |
5/16” |
- |
58% |
0.146 |
| 121 |
¼” |
3/8” |
- |
40% |
0.310 |
| 122 |
¼” |
7/16” |
- |
30% |
0.436 |
| 123 |
¼” |
½” |
- |
23% |
0.529 |
| 124 |
3/8” |
½” |
- |
51% |
0.205 |
| 125 |
3/8” |
9/16” |
- |
40% |
0.310 |
| 126 |
3/8” |
5/8” |
- |
33% |
0.395 |
| 127 |
7/16” |
5/8” |
- |
45% |
0.265 |
| 128 |
½” |
11/16” |
- |
47% |
0.230 |
| 129 |
9/16” |
¾” |
- |
51% |
0.205 |
| 130 |
5/8” |
13/16” |
- |
53% |
0.178 |
| 131 |
¾” |
1” |
- |
51% |
0.205 |
Elasticity Test—Methodology and Results
Instead of the stiffness of the solid material, the equivalent stiffness of the perforated material was used in the test. By assessing the impact of the perforations, the corresponding effective elastic modulus of the perforated material, E, can be obtained as a function of the elastic modulus of the non-perforated or solid material, E. The effective Poisson’s Ratio, ν, of the perforated material is also obtained. This Poisson’s Ratio can be utilized in instances where it is important to correct for load biaxiality.
Furthermore, the effective elastic constants described here are applicable to plane stress conditions, and also relevant to the in-plane loading of the thin perforated sheets of interest. In such perforated sheets, the bending stiffness is slightly greater. But a majority of the loading conditions involve a combination of stretching and bending. It is also easier to utilize the same effective elastic constants for the collective loading conditions.
In addition, the plane stress effective elastic constants presented here can conventionally be used for all loading conditions. The use of these effective elastic characteristics will allow the designer to establish the deflections of the perforated sheet for any loading conditions and any geometry of application, with the help of the available elastic solutions. Hence, the designer can easily establish the extra thickness of the perforated material that will offer equal stiffness as that of a non-perforated material.
O’Donnell and Associates conducted the strength tests that have been made available by the Industrial Perforators Association.