MIL-HDBK-5: Chapter 2.8 — Element Properties
Chapter 2.8 Contents
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Chapter 1 — General Chapter 2 — Steel 2.1 — General 2.2 — Carbon Steels 2.3 — Low-Alloy Steels 2.4 — Intermediate Alloy Steels 2.5 — High Alloy Steels 2.6 — PH & Transformation Hardening 2.7 — Austenitic Stainless Steels 2.8 — Element Properties Chapter 3 — Aluminum Chapter 4 — Magnesium
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For reference use only. The formulas, graphs, and values herein are provided in good faith for general engineering guidance. Please verify all data against MIL-HDBK-5J or the applicable superseding document (MMPDS).

Figures and Tables
Table of Figures
Table of Figures Cont.
2.8Element Properties
2.8.1Beams

See Equation 1.3.2(c), Section 1.5.2.5, and References 2.8.1.1(a) and (b) for general information on stress analysis of beams.

2.8.1.1Simple Beams

Beams of solid, tubular, or similar cross sections, not subject to instability (buckling, crippling, column, lateral bending) can be assumed to fail through exceeding an allowable modulus of rupture in bending, Fb, the value of which will depend upon beam cross-section geometry and beam material stress-strain characteristics. The modulus of rupture in bending is further discussed in Section 1.5.2.5. See Reference 2.8.1.1.

Round Tubes — For round tubes, the value of Fb will depend on the D/t ratio, as well as the ultimate tensile stress. Figures 2.8.1.1(a) and (b) give the bending modulus of rupture for round alloy-steel tubing.

Figure 2.8.1.1(a). Bending modulus of rupture for round low-alloy steel tubing.

Figure 2.8.1.1(b). Bending modulus of rupture for round high-alloy steel tubing.

Unconventional Cross Sections — Sections other than solid or tubular should be tested to determine the allowable bending stress.

2.8.1.2Built-Up Beams

Built-up beams usually fail because of local failures of the component parts. In welded steel tube beams, the allowable tensile stresses should be reduced properly for the effects of welding.

2.8.1.3Thin-Web Beams

The allowable stresses for thin-web beams will depend on the nature of the failure and are determined from the allowable stresses of the web in tension and of the flanges and stiffeners in compression.

2.8.2Columns
2.8.2.1General

The general formula for primary instability is given in Section 1.3.8. Both primary and local instability are discussed in Section 1.6.

2.8.2.2Effects of Welding

The primary failure stress of a column having welded ends can be determined from column curves or the column formula with the restriction that the column stress will not exceed a "cut-off" stress which accounts for the effect of welding on the local failure of the column.

2.8.3Torsion
2.8.3.1General

The torsion failure of steel tubes may be due to material failure, or to elastic or plastic buckling. Pure shear failure usually will not occur within the range of wall thickness commonly used for aircraft tubing.

2.8.3.2Torsion Properties

The curves of Figures 2.8.3.2(a) through (j) are derived from the method outlined in Reference 2.8.3.2 and take into account the parameter L/D; the theoretical results set forth in Reference 2.8.3.2 have been found to be in good agreement with the experimental results.

Figure 2.8.3.2(a). Torsional modulus of rupture—plain carbon steels Ftu = 55 ksi.

Figure 2.8.3.2(b). Torsional modulus of rupture—low-alloy steels treated to Ftu = 90 ksi.

Figure 2.8.3.2(c). Torsional modulus of rupture—low-alloy steels heat treated to Ftu = 95 ksi.

Figure 2.8.3.2(d). Torsional modulus of rupture—low-alloy steels, heat treated to Ftu = 125 ksi.

Figure 2.8.3.2(e). Torsional modulus of rupture—low-alloy steels heat treated to Ftu = 150 ksi.

Figure 2.8.3.2(f). Torsional modulus of rupture—alloy steels heat treated to Ftu = 180 ksi.

Figure 2.8.3.2(g). Torsional modulus of rupture—alloy steels heat treated to Ftu = 200 ksi.

Figure 2.8.3.2(h). Torsional modulus of rupture—alloy steels heat treated to Ftu = 220 ksi.

Figure 2.8.3.2(i). Torsional modulus of rupture—alloy steels heat treated to Ftu = 240 ksi.

Figure 2.8.3.2(j). Torsional modulus of rupture—alloy steels heat treated to Ftu = 260 ksi.

Other MIL-HDBK-5 Chapters
Chapter 1 (General) Chapter 3 (Aluminum)

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