Treesearch

The objective was to determine the relationship between the variables specific gravity (SG) and flake alignment and the dimensional stability properties of flakeboard. Boards manufactured without a density gradient were exposed to various levels of relative humidity and a vacuum-pressure soak (VPS) treatment. Changes in moisture content (MC), thickness swelling, and linear expansion were measured and used to develop regression equations. Under board saturation conditions resulting from VPS, dimensional movement could be defined as a function of SG without regard to MC. The relationship...

An impact stress wave was induced in the end of 2 by 6 lumber containing knots. Rather than a normal, perpendicular-to-the-axis profile in transiting by a knot, the stress wave tended to Iead in zones of clear wood in the direction of the slope of grain or slope of the annual rings and to lag behind the knot. Of three methods evaluated to time the stress wave, the "average" timing method was more consistent than other methods in flagging the 6-inch length containing a knot from adjacent clear wood 6-inch lengths. Stress wave modulus of elasticity (ESW) calculaled from the data tended to be...

Water prehydrolysis of aspen wood was compared with 0.40% sulfuric acid prehydrolysis at a reaction temperature of 170°C. Acid prehydrolysis gave much higher yields of total anhydroxylose units in the prehydrolyzate and removed significantly less anhydroglucose from the wood than did the water treatment. At maximum yields of total anhydroxylose units in the prehydrolyzates, much more monomeric xylose was present in the acid prehydrolyzate than in the water prehydrolyzate.

Woods from abroad are an important raw material to the forest products industries in the United States. A major concern in effective utilization of this resource is the lack of technical information on many species. This report presents the results of an evaluation of the mechanical properties of small, clear specimens of seven Colombian woods. These results are supplemented by information gleaned from world literature concerning other wood properties also important to effective utilization.

A total of 180 small Douglas Fir–Larch (DF-L) or Southern Pine (SP) glued-laminated beams were evaluated to determine the tension lamination quality necessary to obtain desired design stresses. The test beams had either the regular laminating grades of L1 DF-L/No. 1D SP or the special 302-24 laminating grade as tension laminations. Because an initial set of SP beams did not provide valid strength data due to a high frequency of finger-joint failures, a second set of SP test beams was manufactured. Although the initial set of SP beams could not be used to answer the objectives of this...

A computer analysis with user guidelines to analyze partially continuous multi-span beams is presented. Partial continuity is due to rotational slip which occurs at spliced joints at the supports of continuous beams such as floor joists. Beam properties, loads, and joint slip are input; internal forces, reactions, and deflections are output.

Dynamic tests for determining the formaldehyde emission behavior of UF-bonded boards involve the measurement of formaldehyde concentration in the air within a vessel which contains a specified board loading L (m2 of board area per m3 of vessel free volume) and is being ventilated at a specified air exchange rate N (hr.-1). Such tests constitute a primary characterization of board emission behavior since they model conditions for air contamination in dwellings containing those boards. Many other board emission tests, e.g. Desiccator, Perforator, must be regarded as secondary tests since...

A summary of modulus of elasticity (MOE) and knot data is presented for grades of lumber commonly used to manufacture glued-laminated (glulam) timber by the laminating Industry. Tabulated values represent 30 different studies covering a time span of over 16 years. Statistical estimates of average and near-maximum knot sizes as well as mean and coefficient of variation for MOE are given. Modulus of elasticity values are compared with those published for design. Results will be helpful to organizations preparing and evaluating specifications for glulam timber.

Many techniques have been devised to reduce the tendency of wood to change dimensions in contact with moisture. Treatments such as cross-lamination, water-resistant coatings, hygroscopicity reduction, crosslinking, and bulking are reviewed and recommendations for future research are given.

The importance of considering individual machine contribution to total mill efficiency is discussed. A method for accurately calculating machine contribution is introduced, and an example is given using this method. A FORTRAN computer program to make the necessary complex calculations automatically is also presented with user instructions.