PERF HANDBOOK - Elastic Properties of Perforated Metals
Elastic Properties of Perforated Metals There are many potential new applications where perforated materials could be used. In many of these uses, however, the strength and stiffness properties of the perforated sheet are very important. The following information covers the stiffness properties for the standard 60° degree triangular penetration patterns. Since perforated materials can potentially be used in so many applications involving different geometries, materials and loading conditions, design data are given in a very general form. The ratio of the effective elastic modulus of the perforated material, E*, to the elastic modulus of the unperforated material, E, and the effective Poisson's Ratio, v*, are given. These values are given for all the Standard IPA numbered perforations which cover round holes arranged in the standard 60° degree triangular pattern ranging from .020" to 3/4", and account for more than half of the perforating industry's production.
Equivalent Solid Material Concept The concept of equivalent solid material is widely used for design analyses of perforated materials. As applied herein, the equivalent stiffness of the perforated material is used in place of the stiffness of the solid material. By evaluating the effect of the perforations, the equivalent effective elastic modulus of the perforated material, E*, is obtained as a function of the elastic modulus of the solid or unperforated material, E. In addition, the effective Poisson's Ratio, v*, of the perforated material is obtained. This Poisson's Ratio may be used in cases where correction for load biaxiality is important.
The effective elastic constants presented herein are for plane stress conditions and apply to the in-plane loading of the thin perforated sheets of interest. The bending stiffness of such perforated sheets is somewhat greater. However, most loading conditions involve a combination of bending and stretching, and it is more convenient to use the same effective elastic constants for the combined loading conditions. The plane stress effective elastic constants given herein can conservatively used for all loading conditions. Using these effective elastic properties, the designer is able to determine the deflections of the perforated sheet for any geometry of application and any loading conditions using available elastic solutions. It is therefore easy for the designer to determine what additional thickness of the perforated material will provide stiffness equal to that of unperforated material.
Effective Elastic Properties for IPA Standard Perforations