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Formed 0.080 in 2024-T3 angle tension clip with one 1/4 in bolt: leg bending, prying and margins from mechanics

Tool	Tension Clips and Fittings
Source	National Aeronautics and Space Administration (1975). Astronautic Structures Manual, Volume 1. NASA Technical Memorandum X-73305, George C. Marshall Space Flight Center, Huntsville, AL. Section B4.5, eq. (4.5.0-1) (plastic bending modulus of rupture) and Table B 1.1.3.1 (bolt strengths); Chambers, J. A. (1995). Preloaded Joint Analysis Methodology for Space Flight Systems. NASA Technical Memorandum 106943, eq. (56).
Level	Professional

Problem

A single formed angle clip of 0.080 in 2024-T3 sheet (F_tu 64 ksi, F_ty 47 ksi, F_su 39 ksi), 1.5 in wide, carries an ultimate tension load of 120 lb through one 1/4 in bolt in its outstanding leg. The bolt is 0.50 in from the back of the attached leg and 0.40 in from the toe; the inside bend radius is 0.16 in, the washer 0.50 in and the hole 0.257 in in diameter. Two No. 10 steel bolts 0.60 in below the heel attach the other leg. With a fitting factor of 1.15, the leg taken as fixed-guided and a 30° load spread, find the leg moments, the prying force, the bending stresses and the margins of safety.

Inputs to Enter

Angle clip, single; P = 120 lb entered as an ultimate load; FS 1.5, FS_yld 1.15, fitting factor 1.15
t_c 0.080 in, width per bolt 1.5 in, bolt gauge 0.50 in, bend radius 0.16 in, bolt to toe 0.40 in, spread angle 30°, leg model fixed-guided
Hole 0.257 in, washer 0.50 in, bolt tension allowable 4,080 lb; 2 fasteners, 2,125 lb shear and 2,210 lb tension each, 0.60 in from the heel
E 10.5 Msi, F_tu 64 ksi, F_ty 47 ksi, F_su 39 ksi, shape factor 1.5, f_0 blank (F_ty used), k_y 1.0

Open the Tension Clips and Fittings tool (loaded with this example)

Answers

T_u = 1.15 · 120 = 138 lb, T_y = 105.8 lb; F_b = 64 + (1.5 − 1) · 47 = 87.50 ksi
e_h = 0.50 − 0.08 − 0.16 = 0.260 in, w_e = 0.50 + 2 · 0.26 tan 30° = 0.8002 in, net 0.5432 in
Fixed-guided: M_h = Q a = T e / 2 = 17.94 lb-in, Q = 44.85 lb, bolt load B = 182.9 lb (cantilever 138.0 lb, elastic tee-stub 167.6 lb, heel-toe lever 227.7 lb)
Outstanding leg 21.02 ksi at the heel and 30.96 ksi at the bolt line; attached leg M_a = 45.54 lb-in, 2.156 ksi tension + 53.35 ksi bending, R_a = 0.643
Pull-through 1.455 ksi; kick load 37.95 lb and shear 69 lb per fastener; leg mechanism limit load 482.3 lb
M.S.: outstanding leg rupture +1.83 (ULT), attached leg rupture +0.55 (ULT), outstanding leg yield +0.98 (LIM), attached leg yield +0.10 (LIM), pull-through +25.80, bolt +21.31, fasteners +27.18 (ULT)

Notes

The tool's default inputs are this clip; press Submit. The case is illustrative, not a printed example: neither NASA TM X-73305 nor AFFDL-TR-69-42 has a tension clip section, and the test-based clip allowables of design manuals are not reproduced. The beam model leaves out the membrane action of a clip that straightens under load, so it is conservative against tests; an entered test allowable is compared on the page. Checked by test_tension_clip_fitting.php (567 checks): the leg statics against a numpy direct-stiffness beam model of 20 seeded tees, the end-pad plate solver of the fitting mode against the Plate Bending library and a numpy Ritz solution, and the page in both unit systems and load levels.