How is shear strength of fasteners determined? Why don industry fastener standards include such values?
Common practice for steel fasteners is to assume shear strength will approximate 60% of minimum tensile strength. Published data in commercial (non-aerospace fields) does not offer much guidance on shear strengths for bolts, screws, or studs. The first reason is that the number of components loaded in shear is considerably less than for tension, compression, bending, or torsion. The primary reason, however, is the difficulty in obtaining accurate test data. Shear testing inherently involves a number of variables. Therefore, tests are less reproducible than testing for such properties as tensile or yield strength. Most shear testing has been by arbitrary procedures that provide empirical results. The greatest need for shear test data is in structures that are riveted, pinned, or bolted, and also where service stresses are actually in shear. Notable examples are found in the aerospace industry.
