Investigation of Failure Behavior in the Thread Contact of Wood Screws during the Pull-Out Process

Abstract

For optimizing wood screws, it is necessary to understand the failure behavior as well as the effect of screw parameters in the thread contact on the withdrawal capacity. The aim of this paper is to investigate the failure behavior of self-tapping wood screws in spruce wood [picea abies (L.)] during the pull-out process. Because this is possible with existing methods to a certain extent only, two analysis techniques used for investigations of chemical anchoring are adapted. The experiments are carried out using five self-tapping wood screws with an outer diameter of 6 mm. The results show that the screw movement observed during the pull-out process is much smaller than the displacement measured by pull-out machines for certification purposes. Another observation is that the failure behavior of different screw types varies with regard to crack formation. Improved understanding of failure behavior will allow for an in-depth investigation of the influence of screw parameters and, hence, for the design of improved wood screws.