Stress concentration

This paper studies the stress concentrations at the root of the threads of a cylinder. A photoelastic analysis using the stress freezing procedure is used to calculate the stress along the cylinder and the stress concentrations at the root of the threads. These values are compared to that of similar cylinders with different threaded configurations. A finite element model is built by using the photoelastic data to find a suitable load distribution along the threaded region. The finite element model predicted results similar to the photoelastic analysis and showed a method of reducing the stress concentrations on the threads by redesigning a pressure ring on the cylinder.

A static stress analysis of a common chain link and a pear-shaped
nng ivas performed using the finite element structural analysis
program SAP IV. The required finite element mesh and loading
inputs were generated by the pre-processing program PRE-SAP- LINK.
This procedure was used to determine the midplane stresses and
displacements in a link and ring of typical sizes and subject to
concentrated fcrces. Stress distributions and displacements were
drawn by hand and by using a Tektronix 4662 Interactive Digital
Plotter, respectively. The results obtained show that for both
link and ring, the numerically largest principal stress and maximum
in-plane shear stress occur on the element directly under an
applied load . The entire procedure was verified by comparing
the results obtained for the common link with experimental results
in the literature and with analytical results obtained using a
mechanics of materials approach. All of the results were in close
agreement.