PRONG TEST AND STRESS DEVELOPMENT DURING CONDITIONING IN RED OAK

ABSTRACT

Lumber must be conditioned to relieve transverse drying stresses. The standard prong test has been used for many decades to determine the conditioning time needed for complete stress relief. However, no work has been directed at the proper procedures or interpretation of this test. The purpose of this study was to obtain initial information on the factors influencing the prong test and stress development. The major factors studied were prong thickness and surface moisture content Data on stress distribution, moisture gradient, and prong response were obtained periodically throughout conditioning of red oak. Slicing, a residual strain release method, was used to obtain the stress distributions. The results demonstrated that the prong response is a function of prong thickness and stress distribution. Additionally, an explanation of how the stresses are altered was proposed. Further studies concerning conditioning schedules need to be performed before standard test procedures can be suggested.

Keywords and Phrases:

• casehardening
• moisture content