Fracture Toughness and Duration of Load Factor I. Six Principal Systems of Crack Propagation and the Duration Factor for Cracks Propagating Parallel to Grain
Keywords:<i>Pseudotstsuga menziessii</i>, static testing, stress intensity factor, notches, notched beams, moisture changes
AbstractCritical stress intensity factors for air-dry Douglas fir were found to be 2200, 2450, 281, 373, 323, and 323 psi ínch for the LT, LR, TL, RL, TR, and RT systems, respectively, where the first letter indicates the direction normal to the crack plane and the second the direction of crack propagation. Long-term load tests with notched beams showed that for the TL system the load duration factor was similar to that applying to modulus of rupture. Moisture changes significantly reduced the mean time to failure of notched beams under dead loads as compared to tests under constant moisture conditions.
Brown, W. F. J., and J. E. Srawley. 1966. Plane strain crack toughness testing of high-strength metallic materials. Special Technical Publication No. 410, American Society for Testing and Materials, Philadelphia.nHald, A. 1952. Statistical theory with engineering applications. John Wiley and Sons, New York.nLeicester, R. H. 1969. The size effect of notches. Proc. Second Australasian Conference on Mechanics of Structures and Materials, pp. 4.1-4.20.nLeicester, R. H. 1972. Contemporary concepts for structural timber codes. Seminar on Timber Design and Construction in the 70's. University of Auckland, New Zealand.nLeicester, R. H., and P. C. Bunker. 1969. Fracture at butt joints in laminated pine. For. Prod. J. 19(2):59-60.nLi, C. C. 1964. Introduction to experimental statistics. McGraw-Hill, New York.nMadsen, B. 1972. Duration of load tests for wood in tension perpendicular to grain. Structural Res. Ser., Rep. No. 7, Dep. Civil Engineering, Univ. British Columbia, Vancouver, B.C.nPearson, R. G. 1972. The effect of duration of load on the bending strength of wood. Holzforschung 26(4):153-158.nSchniewind, A. P. 1967. Creep-rupture life of Douglas-fir under cyclic environmental conditions. Wood Sci. Technol. 1(4):278-288.nSchniewind, A. P., and D. E. Lyon. 1973. A fracture mechanics approach to the tensile strength perpendicular to grain of dimension lumber. Wood Sci. Technol. 7(1):45-59.nSchniewind, A. P., and R. A. Pozniak. 1971. On the fracture toughness of Douglas fir wood. Eng. Fract. Mech. 2(3):223-233.nTomin, M. 1972. [Measuring fracture toughness of wood]. Drevarsky Vyskum 17(4):215-230.nWalsh, P. F. 1971. Cleavage fracture in timber. Div. For. Prod., CSIRO, Tech. Paper No. 65, Melbourne, Australia.nWalsh, P. F. 1973. The interaction of butt joints. J. Inst. Wood Sci. 6(2):22-27.n
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