Influence of drying/conditioning schedules on stress development, relief and prong test

The prong test often displays ambiguous responses as shown in recent resear ch. The objective of this paper was to learn how different drying/condition ing schedules influence the stress development/relief of lumber and therefo re the prong response. During each drying/conditioning schedule, residual s tress analysis was used to obtain stress levels, moisture content gradients and prong responses. The analysis of the data revealed the following: stre ss levels are strongly influenced by different schedules; in contrast, pron g responses are only slightly influenced by different schedules. Stress lev els are more effectively relieved by using a multiple- step increase of the equilibrium moisture content than a single-step increase. It is concluded that the schedule governs the final stress level. Even though differences i n stress level are measurable by the slice test, the prong test does not re liably display these differences.