The influence shank area on the tensile impact strength of bolts
"The effect of reduction of shank cross-sectional area on the tensile impact strength of 5/16, 3/8, and 7/16-in. steel bolts was investigated experimentally. Low-carbon 3/8-in. bolts with rolled threads absorbed maximum impact energy when the ratio of shank area to thread-root area was equal to 1.23. Heat-treated medium-carbon 3/ 8-in. bolts absorbed maximum impact energy when the ratio of shank area to thread-root area was equal to 1.17 for shanks reduced by drilling or 1.12 for shanks reduced by turning. Results for other sizes were similar. It was concluded that for maximum energy absorption the shank area should approximately equal the mean or tensile-stress area of the threads, with minor corrections to compensate for work hardening due to thread rolling or surface oxidation resulting from heat-treatment."--Page 1489.