FASTENER
PULL-THRU STRENGTH
(MIL-STD-1312-8A)
Model No. CU-PS (low carbon
steel)
Model No. WTF-PS (17-4PH stainless)
This test
method, as defined by MIL-STD-1312-8A (Reference 1), was originally
intended for use in determining the tensile strength of fasteners.
However, its use has been broadened to include pull-thru strength,
i.e., the strength of the plates the fastener is holding together.
Specifically, the pull-thru characteristics of mechanically fastened
composite plates (joints) have been standardized in MIL-HDBK-17
(Reference 2).
There are a
number of fixture configurations in use. One commonly used
configuration, specified in Reference 1, is shown in the photograph
below.
Fastener
Pull-Thru Strength Fixture – Top and Bottom Halves
The test specimen consists of two
1.5” square plates connected at their centers by the desired
fastener being tested. The plates are rotated 45 degrees relative
to each other, so that the eight corners are all individually
exposed. The two pins and indexing holes shown in the photograph
maintain proper rotational alignment of the two halves of the
fixture. The bottom half of the fixture contacts the four corners
of the top plate and the top half of the fixture contacts the four
corners of the bottom plate. When a compressive force is applied to
the assembled fixture, the fastener becomes loaded in tension. The
force required to cause the fastener to pull through a plate is the
desired result. Testing details are given in Reference 1.
The above
fixture permits the use of a simple test specimen, requiring only
one (fastener) hole in each plate. Other fixture configurations are
also available, utilizing specimen plates of various sizes. These
fixtures typically require multiple holes in each specimen plate,
adding to the complexity of specimen fabrication. Two such fixtures
are presented in References 1 and 2, respectively.
Sources of
Additional Information:
1)
1)
