Machinery's Handbook, 31st Edition
Strength and Stiffness of Perforated Metals 2705 Strength and Stiffness of Perforated Metals.— It is common practice to use perforated metals in equipment enclosures to provide cooling by the flow of air or fluids. If the perfo rated material is to serve also as a structural member, then calculations of stiffness and strength must be made that take into account the effect of the perforations on the strength of the panels. The accompanying table provides equivalent or effective values of the yield strength S *; modulus of elasticity E *; and Poisson’s ratio ν * of perforated metals in terms of the values for solid material. The S */ S and E */ E ratios, given in the accompanying table for the standard round hole staggered pattern, can be used to determine the safety margins or deflections for perforated metal use as compared to the unperforated metal for any geometry or loading condition. Perforated material has different strengths depending on the direction of loading; there fore, values of S */ S in the table are given for the width (strongest) and length (weakest) directions. Also, the effective elastic constants are for plane stress conditions and apply to the in-plane loading of thin perforated sheets; the bending stiffness is greater. However, since most loading conditions involve a combination of bending and stretching, it is more convenient to use the same effective elastic constants for these combined loading condi tions. The plane stress effective elastic constants given in the table can be conservatively used for all loading conditions. Mechanical Properties of Materials Perforated with Round Holes in IPA Standard Staggered Hole Pattern Length of Sheet Standard 60° Staggered Pattern
S */ S
IPA No. 100 106 107 108 109 110 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128
Perforation Diam. (in.)
Center Distance (in.)
Open Area (%)
Width (in.)
Length (in.)
E */ E 0.565 0.529 0.246 0.362 0.395 0.529 0.342 0.310 0.436 0.529 0.249 0.362 0.205 0.395 0.146 0.310 0.436 0.529 0.205 0.310 0.395 0.265 0.230
ν *
0.020
(625)
20 23 46 36 32 23 36 40 29 23 46 36 51 33 58 40 30 23 51 40 33 45 47 51
0.530 0.500 0.286 0.375 0.400 0.500 0.360 0.333 0.428 0.500 0.288 0.375 0.250 0.400 0.200 0.333 0.428 0.500 0.250 0.333 0.400 0.300 0.273 0.250
0.465 0.435 0.225 0.310 0.334 0.435 0.296 0.270 0.363 0.435 0.225 0.310 0.192 0.334 0.147 0.270 0.363 0.435 0.192 0.270 0.334 0.239 0.214 0.192
0.32 0.33 0.38 0.35 0.34 0.33 0.35 0.36 0.33 0.33 0.38 0.35 0.42 0.34 0.47 0.36 0.33 0.33 0.42 0.36 0.34 0.38 0.39
1 ∕ 8
1 ∕ 16 5 ∕ 64 5 ∕ 64 3 ∕ 32 3 ∕ 32 1 ∕ 10
7 ∕ 64
1 ∕ 8
5 ∕ 32 3 ∕ 16 5 ∕ 32 3 ∕ 16 7 ∕ 32
1 ∕ 8 1 ∕ 8 1 ∕ 8
1 ∕ 4
7 ∕ 32
5 ∕ 32 5 ∕ 32 3 ∕ 16 3 ∕ 16
1 ∕ 4 1 ∕ 4
5 ∕ 16 5 ∕ 16
1 ∕ 4 1 ∕ 4 1 ∕ 4 1 ∕ 4 3 ∕ 8 3 ∕ 8 3 ∕ 8
3 ∕ 8
7 ∕ 16
1 ∕ 2 1 ∕ 2
9 ∕ 16
5 ∕ 8 5 ∕ 8
7 ∕ 16
11 ∕ 16
1 ∕ 2
129 0.42 Value in parentheses specifies holes per square inch instead of center distance. S */ S = ratio of yield strength of perforated to unperforated material; E */ E = ratio of modulus of elasticity of perfo- rated to unperforated material; ν * = Poisson’s ratio for given percentage of open area. IPA is Industrial Perforators Association. 9 ∕ 16 3 ∕ 4 0.205
Copyright 2020, Industrial Press, Inc.
ebooks.industrialpress.com
Made with FlippingBook - Share PDF online