Comparison of nondestructive testing methods for evaluating No. 2 Southern Pine lumber: Part B, modulus of rupture

Abstract

The identification of strength-reducing characteristics that impact modulus of rupture (MOR) is a key differentiation between lumber grades. Because global design values for MOR are at the fifth percentile level and in-grade lumber can be highly variable, it is important that nondestructive evaluation technology be used to better discern the potential wood strength. In that manner, higher-performance pieces could potentially be identified and their value captured accordingly. In this study, laboratory tests of three nondestructive testing (NDT) technologies and destructive four-point static bending were applied to 343 pieces of visually graded No. 2 southern pine lumber in the 38 X 140 mm² (n=86), 38 X 186 mm² (n=112), 38 X 236 mm² (n=91), and 38 X 287 mm² (n=54) sizes collected across the southeast region of the United States. The NDT tests included continuous lumber test in continuous proof bending (MetriguardModel 7200 High Capacity Lumber Tester), transverse vibration (Metriguard E-Computer), and two longitudinal stress wave tools (Falcon A-Grader and Fiber-gen Director HM200). Following nondestructive tests, the specimens were destructively tested in four-point static bending. Single-predictor linear correlations were observed between static bending MOE and MOR value; and NDT outputs and bending MOR value. The regression results showed that the average NDT outputs (r² = 0.23-0.28) had lower performance than static bending MOE (r² = 0.39), for predicting the bending MOR of sawn lumber.

Citation

Yang, B.Z.; Seale, R.D.; Shmulsky, R.; Dahlen, J.; Wang, X. 2017. Comparison of nondestructive testing methods for evaluating No. 2 Southern pine lumber: Part B, modulus of rupture. Wood and Fiber Science. 49(2): 134-145.