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. This method is more suitable for hardwood spp.

Resistance depending upon the shape of the nail, Precaution: put nail always at a right angle, Moisture content affects greatly to the nail strength property, NWR is directly proportional to the density. 3. The deviation or the slope in grain from the straight alignment that may be due to disturbing conditions during the growth of the tree is considered a natural defect for construction purpose because many properties of timber are related to the grain. The temperature has an impact on the strength of wood. Straight-grained timber is considered best, other things being the same. Here moisture content is measured indirectly by measuring other properties. This method is more accurate as compared to oven dry method. The standardized size used for this test is (5cm 5cm 5cm), Compression is perpendicular to grain at E.L = Load at E.L / Area (kg / cm, The size of the test piece is 30cm 2cm 2cm. Here the percentage of water is calculated as compared to green wood. The extent of deformation will depend on the direction in which it has been cut with respect to the grain of the tree. The taste of wood is greatly related to the odor probably traced to the same constituents. The heat conductivity of wood is reduced when the moisture content percentage rises. Colour covers a wide rangeyellow, green, red, brown, black, and nearly pure white woods exist, but most woods are shades of white and brown. For dry woods, error possibility is 2% of moisture content while for green wood error may be 1.5%. But the advantage is that it is a rapid method completes in 3-4 hours. 6. The color of wood may be changed due to any fungal attack on timber. But what is the density of wood? When the density or specific gravity of the wood is less than 0.36, it is referred to as light wood. Hygrometer has very simple construction it contains a metallic plated over which two thermometers are attached. In general, latewood, because of its thicker cell walls and smaller cell cavities, is denser than earlywood, and with increasing ring width its proportion decreases in softwoods and increases in ring-porous hardwoods. Moreover, the higher amount of water in the cells invites many fungal and insect growths which destroy the wood tissue. This is the case when we have to find out the density of regular shape. The beaker is generally graduated in centimeter or cubic centimeter. EMC is defined as, , Whenever softwoods are dried from Fiber Saturation Point to oven dry condition. 2. The color of wood also changes when we observe tree from down to upward direction. After initial weighing, the sample wood should be transferred to the oven or drying oven. Shrinkage for common hardwood spp is from FSP (25 30%) to EMC (12% moisture content.) As regards odor (smell), quite a few kind of woods are immediately identified by their characteristic smell. m.c % = w1 w2 / w2 * 100Where; w1 = w.t of a piece of wood with certain moisture content; w2 = w.t of that piece of wood after oven drying. The color of wood also change4s by applying different chemical on it. But the colour of the wood varies from type to type. These supplementary macroscopic characteristics are helpful in describing a piece of wood for identification or other purposes. (one cubic cm = one gm). Let's see more interesting facts about wood, different physical, chemical, mechanical, properties of wood. It is known that in the drying process, moisture from the wood is lost first from the cell cavity and then from the cell walls. Lustre - Another physical property of wood is its lustre. Moisture meters have a max capacity of measuring moisture up to 100%. The same can be said for heat conductivity. The most important fact about the strength of timber is that it is not the same in all directions. Other expressions of density, such as those based on air-dry weight and volume or on weight and volume of green wood, have a certain practical importance, as in shipping wood, but are not accurate. The density of a sample of wood can be appraised visually by observing the width (thickness) of growth rings and the proportion of latewood. Wood is a very light material, its specific gravity being always less than 1 (that of water). Youll learn in details about the Properties of Wood and Timbers here. Finally the density of the wood taken. CASE III: Oven dry condition calorific heat value is 2-3 times greater than the CASE I, below the FSP ie at 0% moisture content. On heating, vapors come in condenser after passing from glass tube attached to flask. The relative humidity can be calculated as shown in the table: Relative Humidity is now plotted in the graph with moisture content. Odour and taste are due to volatile substances contained in wood.

By grain, it is understood that the arrangement and direction of growth of the wood elements (tracheids, fibers, and vessels) in the wood.

CBSE Previous Year Question Paper for Class 10, CBSE Previous Year Question Paper for Class 12. These factors are known as risk factors of wood. 3. 0 These properties explain the characteristics of wood with a generalized meaning. It is because in the latter case full width of the cell walls is involved. 8. The shine of the wood takes precedence over the colour. The strength of wood also gets affected by the temperature. The selection of the piece should be done very carefully. But what is the density of wood? In diffuse-porous hardwoods latewood is not clearly distinct, and ring width is not an indication of density. The conductivity of wood is also affected by its size, structure, and dryness. One pane serving for weight and other for the beaker containing water. If the density or specific gravity is 36 then the wood is called very light. Anatomical structure: Porous wood burns more readily than dense wood. Now calculate the loss in w.t from initial w.t and final w.t, as follow: Then the amount of volatile matter is calculated: The m.c % can be determined by the following formula: For the preparation of Charcoal in improved form, The properties which are observed by applying an external force. Thick walled cells shrink more than the thin-walled cells. After colour, priority is given to the lustre of the wood.

In the radial direction, it is of an intermediate order. Quality gradually improves the passage of time. Heat and electricity do not conduct well through the wood. Below is thorough information on the density of several types of wood. They are explained as follows. Shear is found parallel to grain and perpendicular to grain as well. Although difficult to describe, they are helpful distinguishing characteristics in some cases. The wood with excessive moisture contents has less calorific value and vice versa. It is decided if it is a good conductor of electricity or a bad conductor of electricity based on its capabilities. Based on its ability, it is determined whether it is a good conductor of electricity or a bad conductor of electricity. In this method, 50 gm of chips or sawdust are taken into a round bottom flask. He is the CEO of Tech Urdu (techurdu.net) Forestrypedia (forestrypedia.com), All Pak Notifications (allpaknotifications.com), Essayspedia, etc & their YouTube Channels). The weight of the hammer is 8.5 kg. The rate of heat flow through the wood sample is also determined by the direction and density of the wood sample. It may be carefully noted that the value of compression at the elastic limit (before deformation) is different from that value of maximum load (after deformation). For a parallel to the grain size of the test, the piece is 5-inch 2-inch 2 inch. When the density or specific gravity of a piece of wood is 36, it is referred to as "extremely light.". Energy or work = w = F D = 8.5 1.2 = 10 m/kg, Here energy means the striking energy of hammer. That level of moisture content of timber is called equilibrium moisture content.. It may vary from 300 to 900 km/cm2 or more. But the strength of wood can be affected by various factors. The density of wood is for various types of wood samples. (Expressed as weight per unit volume, 1 gram per cc is about 62.4 pounds per cubic foot.). While weight may be varied this is usually 2% of sample or 20gm. Different types of physical properties and mechanical properties of wood explain the characteristics of a particular type of wood. Hardness and strength of wood depend to a great extent on its density. Units: The calorific heat value is expressed in: iii) Btu/ lb or, British thermal unit/ pound(1 Btu = 252 calories). There are a variety of standards for determining the strength of wood. Therefore determination of moisture is very important. When cutting and exposed to the atmosphere, a balance may be achieved between the moisture in the atmosphere (humidity) and the wood. Theodolite Parts and Functions [A Detailed Guide]. 4. If there is no sample in way of a hammering than the amount of striking energy is 10 meters/kg. For example, the sandalwood and the rosewood give a nice aroma whereas the other timber woods may give some tobacco odour. Dryness of wood: Moisture contents affect the heat/ calorific value of wood. Eg liming lightens the color etc. 497 0 obj <> endobj Only when the walls become saturated, water goes to the cell cavities. Than establishment of data, from this data proper use is estimated. Shafiullah. The shine of wood is another physical characteristic. Wood is termed moderately heavy if its density or specific gravity is between 0.36 and 0.05. For example, the sandalwood and the rosewood give a nice aroma whereas the other timber woods may give some tobacco odour. After the complete combustion of that piece of wood, weigh the amount of ash leaving behind. A piece of wood with certain moisture contents.

Name Some Factors that Affect the Strength of the Wood. Rate of load applied is 60mm / sec or 1-2 minutes / test, Max compression parallel to grain = Maximum load / cross-sectional area = kg/cm, Compression parallel to grain up to elastic limit = load at E.L / area = kg/cm. As sensory characteristics, weight and hardness are included in a diagnostic rather than technical senseweight as judged by simple hand-lifting and hardness by pressing with the thumbnail. The thermal and electrical properties of wood explain the conductivity of wood. Bad smelling wood should not be used as food containers. Similar is the case which we apply load on wood. Grain signifies arrangement and direction of fibers and vessels in the wood: parallel to the trunk, oblique to the trunk or turned and twisted with respect to the longitudinal direction of growth. if so, for what reasons? Its increased volume in the cell simply decreases the volume of the wood tissue. In the metric system of measurement, density and specific gravity are numerically identical; for example, the average density of the wood of Douglas fir is 0.45 gram per cc, and its specific gravity 0.45, because 1 cc of water weighs 1 gram. Wood that has been lying in the air for quite some time (six months to one year) after felling, however, loses most of its moisture to the atmosphere. Wood's Mechanical Properties The ability of wood to endure externally applied forces can be defined as its mechanical characteristics. Size of a piece of wood: Smaller the piece of wood used the quicker the combustion process and greater heat is given out in short time, and vice versa. The most effective way to lose weight naturally is by acquiring it slowly and gradually and obeying some basic points which can enable you to make the most from a attempt to lose weight. This type of structure is called a straight grain. Presence of extraneous substance: The presence of extraneous/ inflammable/ organic substances such as resin, etc increase the combustibility of wood. Ie, Density = weight / volume. Wood conductivity is explained by its thermal and electrical properties. Moisture is contained in timber as free moisture in cell cavities and as imbibed moisture in cell walls. Density is usu obtained by dividing weight/mass by volume. Density: Higher the density of timber, greater will be its strength. Importance of color is from a decorative point of view and use for the identification of wood.Following factors affect the luster of wood: % of humidity = (Dry wood molecules / fully saturated molecules) 100= (Dry vapor of air / saturated vapor of air) 100, Shrinkage in the longitudinal direction = 00.1 percentShrinkage along radial direction = 5%Shrinkage along tangential direction = 10%, % age = [Dim t(max) Dim t(min)] / Dim t(max) 100. We can classify wood into four groups whenever we take into consideration moisture contents: MC % = (initial w.t of sample final wt) / final or dry wt of sample 100MC % = w1 w2 / w2 100, Definition: The minimum amount of heat required to evaporate the unit mass of water.In the wood of excessive moisture contents (EMC), the most of the heat is utilized to evaporate the moisture content within the wood and this phenomenon is known as lowering the heat of combustion.The case I: In the air dry wood, the evaporation of moisture along with the combustion with the release of gases takes place.Case II: In the oven dry wood the combustion takes place with the maximum release of heat (due to minimum moisture contents within it).The calorific heat value in all of our indigenous spp range from 4500 5500 kcal/kg. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); Naeem Javid Muhammad Hassani is working as Conservator of Forests in Balochistan Forest & Wildlife Department (BFWD). If we take electric conductivity, it is the capability of wood to conduct and let electricity pass through it. This in turn affects the strength of the wood. But gradually disappears with the passage of time. endstream endobj startxref Different scents and tastes are regularly observed from various types of wood. With each inspection, the colour of the wood changes. Preservation of Timber and Wood. The density of irregular shapes may be found by following two methods: First of all initial reading of mercury is taken. The chief conditions that affect the heat value of wood are: The following procedure is adopted for the determination of ash contents of a wood. They are -, Compression - The compression of wood depends on the directions of applied forces, like -. The density of Wood - Another characteristic of wood is its density. Actually, bulb of that thermometer is supplied with vapors so that it can calculate net temperature. He is an Environmentalist, Blogger, YouTuber, Developer & Vlogger.