• Version
• 304 Downloads
• 1.37 MB File Size
• 1 File Count
• December 4, 2015 Create Date
• December 4, 2015 Last Updated

National Advisory Committee for Aeronautics, Technical Notes - Analytical and Experimental Investigation of Bolted Joints

Results are given of an analytical and experimental investigation
of stresses in symmetrical butt Joints. The methods of analysis,
which are based on the preliminary investigation of NACA 'IN No. 1051,
are presented. in the first part of the paper. A recurrence formula
is developed-'uhich in conjunction with the appropriate 'boundary
equations can be used to- obtain sets offisimultaneous linear equations
the solutions of which result in the bolt-load distribution for.
Joints of uniform dimensions with .bolts in line with the load its
procedure is also given in which the recurrence formula is applied
as a homogeneous finite difference equation of the second order.

In addition, an approximate. analysis based on the shear-lag solution
of a substitute single stringer structure is presented which may be
employed in most practical designs with some gain in time at a small
sacrifice in accuracy. An example is solved to demonstrate the use
of the shear-lag solution and a comparison is made with the other
methods of analysis.

The second part of the paper describes strain-gage tests for
Joints with five and nine bolts in line. (The preliminary investi-
gation analyzed joints with only three bolts in line.) Because of
the generally satisfactory agreement obtained in these static tests
it appears probable that this analysis may serve as an adequate.
basis of design of Joints Subject to fatigue loads.

In a preliminary investigation of bolted Joints the inadequacy
of the elementary engineering formflas for the stress analysis of
bolted Joints within the elastic and plastic ranges, but excluding
failure, was clearly indicated. In this investigation (reference 1)
a. method was developed for calculating the loads carried by the
individual belts in eynnnetrical butt Joints- The general bolt-load
behavior in the elastic range for Joints was given as an equation
which expresses the relationship between the loads on any two
successive belts in line with the load. Although this expression
is applicable to Joints'of variable bolt spacings, stiffnesses,and
materials, its application is somewhat tedious, especially in the
case of long joints.