CET 345W Materials Testing Laboratory Experiment No. 2 Compression and Flexure Test of Wood

1. Summary Wood is an anisotropic material meaning that it behaves differently in all different directions. It is made of cells referred to as fibers. These cells vary in length depending on the type and species of wo ...

1. Summary Wood is an anisotropic material meaning that it behaves differently in all different directions. It is made of cells referred to as fibers. These cells vary in length depending on the type and species of wood. Generally, the many different species of wood are separated in to two different groups of hardwoods and softwoods. Hardwoods are usually those who lose their leaves in the fall and softwoods are usually evergreen. Wood also has growth rings that normally represent one year of growth and represent both springwood, which is composed of fibers having large cells and thin walls, and summerwood, which is composed of smaller cells and thicker walls. Another property of wood is its density and the higher the density the stronger the wood is. Also, wood is a hygroscopic material meaning it will continually take on or give off moisture changing its volume until it reaches equilibrium with its environment. In this experiment we will examine the behavior of wood as it is subject loads in different directions through a series of tests. The ASTM specifies for clear, straight-grained samples with approximate dimensions of 2”x 2.” The pieces of wood will not be ASTM standard because they may have knots or high moisture content but will give comparable results. In the flexure test several modes of failure may be observed including buckling and longitudinal split. In bending the proportional limit of outer fibers will be observed. 2. Procedure I. Observing and Measuring 1. Examine each cross-sectional view of the 6-inch, 9-inch, and 28-inch pieces of wood. Record type of wood, number of rings per inch, and percent summer wood. 2. Sketch 3 different views of the steel block, and the 6-inch, 9-inch, and 28-inch pieces of wood. 3. Zero digital micrometer by selecting the ZERO/ABS button before each measurement. 4. Take measurements with digital micrometer. a. Measure the length and two widths of the steel block 3 times each. b. Measure the length and two widths of the 6-inch piece of wood 3 times each. c. Measure the two widths of the 9-inch piece of wood 3 times each. d. Measure the two widths of the 28-inch piece of wood 3 times each. 5. Take measurements with tape measure. a. Measure length of 9-inch piece of wood 3 times. b. Measure length of 28-inch piece of wood 3 times. 6. Mark at 14 inches and 0.5 inches from end points of the 28-inch piece of wood. II. Testing for Compression Perpendicular to the Grain 1. Place 6-inch piece of wood flatwise on the Tinius Olsen 60K Universal Testing Machine using a steel base plate to elevate the platform. 2. Place a 2-inch-wide steel block across the middle third of the piece of wood, with the long axis of the plate normal to the long axis of the specimen. 3. Program the 602 Controller: a. Select RETURN b. Select PUMP c. Select Hd↓ three times to lower the middle crosshead over the piece of wood.