Tensile Test Lab Report Essays

Tensile Test Lab Report Essays Tensile Test Lab Report Paper Tensile Test Lab Report Paper Introduction The construction materials course is an essential part of civil engineering as the strength of all structures and constructions depends on the material used. The tension test is one of the laboratories which help students develop their knowledge in this course by practice. During the laboratory a Tinnitus Olsen Tension Test equipment was used, and the test samples were from low and high carbon steel and timber with grains parallel and perpendicular to the load. Test equipment and materials The test equipment used during the laboratory is one of the Penchant Materials Testing Machines made by Tinnitus Olsen. This machine can test different types of materials and it is provided with software which gives the opportunity to users to fully control the system. Machine two different types of attachments: the first is to fix the metal samples, and second is to hold timber samples. The rate of loading can be controlled by the software. Brief comments on differences and similarities in each property for the set of materials From the tables above it can be seen that: * Low-carbon steel has the largest load and stress at elastic limit among all materials * High-carbon steel has the largest maximum load and stress among all materials * High-carbon steel has the largest failure load and nominal failure stress among all materials * Low-carbon steel has the largest true failure load among all materials * All properties is larger for timber with grains parallel to the grain rather than for timber with perpendicular to the grain Graphs Stress-strain or load-extension graphs have a different form depending on the structure of material and of these graphs can be divided to two different regions: elastic deformation and plastic. Elastic deformation occurs in the region where the curve behaves linearly and after the removing the load material will return to its initial shape. When the elasticity ends the plastic region begins. In plastic region strain can increase significantly whereas stress increases with smaller increment. If the unloading happens the curve will fall parallel to the elastic region. The Stress-Strain graphs have the same shape as Load-Extension graphs. To prove that the stress-strain curves were sketched for three different types of metal: low-carbon steel, high-carbon steel and aluminum. The data used during plotting the stress-strain graphs is represented in Appendix. The graphs for low- carbon (0. 15%) steel (See Figure 1 2). Figure 2. The stress-strain graph for low-carbon steel It can be seen from the graphs that at the beginning the curve behaves linearly until it reaches approximately 14. Non (See Figure 1). Therefore, this section of the graph can be called the elastic region. Then the plastic region begins, and the curve reaches its maximum point at 15. Ink. After that the load decreases gradually for the bigger increment of extension until the break occurs (at 10. Non). The graphs for High-carbon (0. 4%) steel. Figure 4. The Stress-Strain Graph for High-carbon steel The graph for high-carbon steel is similar to the graph for the low-carbon steel. However, the maximum stress in the graph for high-carbon steel is more by non, and equal to the 19. Non. Also it can be seen that the length of high-carbon steel before the failure is less than for low-carbon steel. The elastic region continues until it reaches 12. Ink, and the plastic region ends when specimen breaks at 16. Ink. The graphs for Aluminum. Figure 6. The Stress-Strain Graph for Aluminum The shape of the curve in the graph is similar to the graphs for the steel. However, it can be noticed that the maximum load for aluminum is much less than for steel. Consequently, the load at elastic limit and fail ure load are also small (5. Ink and 3. Ink respectively). The causes of difference of the graphs will be given in Discussion part. The Figures 7-10 illustrate the tension test for timber samples when the load was applied parallel to the grain. From these graphs it is easy to see that the elastic region is very small for timber. In contrast, the plastic deformation takes the bigger region for the large extension. In addition, the specimens break when the maximum load is applied, and it seems that the failure occurs several times. The cause of this behavior is that all grains do not break at one time. The Figures 11-12 show the load-extension graphs for specimens when the load was applied perpendicular to the grain. It can be seen that the failure occurs at small applied load with comparison to other materials. The elastic regions for these specimens are bigger than for samples parallel to the grain. The extension is very small. The calculation of the mean stress, standard deviation, coefficient of variation and characteristic value The mean stress is the arithmetical average of failure stresses: mom=on 7 Where o is the sum of the failure stresses for timber specimens when the load was applied parallel to the grain, and n is the number of specimens. Amp The standard deviation is the degree of spread about the mean stress and it can be calculated as: so=(o-mom)an (8) Where so is variation, s is the standard deviation and o is the failure stresses. Mama s=9. 44 Amp The coefficient of variation: c=somas 9 The calculated result for coefficient of variation (26. %) for this timber was accurate enough as the coefficient of variation for timber must vary from to 30%. The characteristic stress is: char=mom-KS 10 Where k is the standard deviation multiplication factor, and KS is the margin. There kiss equal to the 1. 64 (1 in 20 failure rate). Discussion Firstly, it was noticed that the properties vary depending on the amount of carbon added to the steel. Adding the carbon increases the strength of steel thereby it makes the steel become more brittle. Therefore, the strain for high- carbon steel is less than for low-carbon one, and the maximum stress of low- carbon steel is less than for high-carbon one. Also as the strain or both low and high carbon steel is more than 5% it can be said that they are ductile materials. Secondly, as the strain for the aluminum specimen is less than 1% it seems that it is brittle material. However, the graphs for brittle materials have a little plastic region or even do not have this region. But there is significant plastic region in the Figure 5. It can be predicted that the main causes of that are the defects in the aluminum specimen and the errors related to the equipment. Thirdly, unlike all other materials the graphs for the timber specimens have upturn before failure. The Figures 7-10 are for the same material as timber with grains parallel to the load; however, these graphs differ from each other. Because all specimens do not have the same structure of grains and have different dimensions, also they can have defects as timber is the natural material. Fourthly, the timber specimens with grains perpendicular to the load are the most brittle among other tested materials. As the grains are not connected strongly the failure load of the specimen is not large. Finally, all of the graphs do not show ideal expectations and the possible sources of error are that the specimens were to fixed properly before the test, the material have the defects (was not homogeneous), reduction of decimal points during calculations and errors of the equipment. Conclusion To sum up, the properties such as elastic limit stress, nominal and true failure stresses, etc. Ere obtained. The graphs of stress versus strain were plotted for each type of metals and the graphs of load versus extension were represented with comments for each specimen. The mean stress, standard deviation, coefficient of variation and characteristic stress were calculated for timber samples with grains parallel to the grain. Also the figures of materials after the allure were sketched. In conclusion, the low-carbon stress is more elastic, and the high-carbon stress is stronger. The timber with grains parallel to the load can hold more load than those with perpendicular.