paraphrase the experiment

Abstract

The “Notched Bar Impact Testing of Materials” is an experiment that requires using of the Charpy Testing Machine. This experiment required group number 4 to examine five samples of each of the 1018 steel and 2024 aluminum when placed under different temperatures for a certain amount of time. These specimens are later transferred to the Charpy machine using the notched-bar impact test to place the specimens in the right position. Moreover, Materials sometimes display brittleness which precludes their use in a given design. Brittleness is characterized by fracturing with low energy under impact. The fracture energy is proportional to the area under the tensile stress-strain curve and is called the toughness. Tough steel is generally ductile and requires 100 ft-lbs of energy to cause failure. Brittle steel does not deform very much during failure and requires less than 15 ft-lbs energy to cause failure. Furthermore, characterizing the toughness of a material is done in many ways. The most common method used is the notched-bar impact test for which two different types of specimens prevail, Charpy and Izod. By subjecting a specimen to an impact load, it will fail if the load exceeds the breaking strength of the material either Steel or Aluminum. By using a swinging pendulum to impart the load, the energy required to fracture the specimen can be calculated by observing the height the pendulum swings after fracture. Therefore, this experiment gave group number 4 the knowledge about the impact energy, width, and shear percentage for each of the samples.

Introduction

There are many steps on experiment number two, which is, (Notched Bar Impact Testing of Materials). For example, testing 1018 steel and 2024 aluminum in the Charpy testing Machine. Moreover, sometimes when materials face frailty or being under pressure that precludes their use in a given design. Brittleness is characterized by fracturing with low energy under impact. For this experiment the main ideas we experienced were:

1- Charpy impact tester, sample positioned in anvil and general testing results.

2- Impact Energy transition from ductile to brittle behavior.

3- Lateral expansion of Charpy impact specimen.

Procedure

The procedure for experiment number 4:

First of all group four had to make sure of the safety and review the safety considerations. Label each specimen using a hammer and punch. Second, identify and measure the initial lateral dimensions of all specimens. Third, conduct impact tests on 5 as received 1018-steel and five 2024-Al specimens heated or cooled to dry ice, antifreeze bath with some dry ice, ice water, boiling water and room temperature. For example results, it is important that all specimens be positioned identically in the anvil of the Charpy impact tester; use the special tongs provided to correctly position the specimen. The notch on the specimen must face 180o opposite to the hammer. Then the engineer student had to measure lateral dimensions after impact. Observe the nature of the fracture surface of steel specimens. The fracture specimens should all be carefully examined and particular attention should be paid to the type of fracture that is obtained in each particular case. Try to relate the type of fracture to the energy absorbed by the metal being fractured. A binocular microscope is available to study these fractures carefully. Look for cleavage and shear and estimate the fraction area of each. Moreover, the group applied the impact test of each of the five 1018 steel samples, as well as the 2024 aluminum samples by placing them under different conditions and temperature. That is place the specimens in dry ice/acetone bath (at -79°C), anti-freeze/ water mix with some dry ice (-40°C), ice water (0°C), room temperature (23°C), and boiling water(100°C) for ten minutes. After all, the group used the notched-bar impact test to place the specimens in the right position. Then record the impact energy and measure and record the lateral dimensions after impact. Last but not least, the group had to examine and analyze the fractures of each of the specimens and look for cleavage and shear, and approximate the fraction area of each of the single sharps.

Results and Discussions

After doing the experiment “Notched Bar Impact Testing of Materials” and applying all the required conditions and tests it is shown that the initial width for both, Aluminum 2024 and steel 1018, were lower than the width measured after the reaction has taken place. The lateral dimensions for each of the steel and aluminum are presented in Tables 1.1 and 2.1 respectively. Moreover, it is also recognized that after applying the impact test, the fracture energy for steel 1018 is higher than that of 2024 Aluminum. Also, it is shown that the shear percentages for the 2024 Aluminum is constant; while for the 1018 steel, it starts to increase as temperatures increases. Furthermore, the variation of impact energy versus temperature for each of the 1018 steel and the 2024 aluminum are shown In addition, Graph 1.2 represents the changes in width versus Temperature for each of the 2024 Aluminum and 1018 Steel. As temperature increases, the change in width slightly decreases for aluminum 2024. While for 1018 steel, the change in width starts low, then when temperature reaches -40°C it starts to increase till reaching 0°C; after this temperature it starts to decrease slightly again.

Conclusion

On experiment number two, which is “Notched Bar Impact Testing of Materials” group number four have gone through a lot of steps in order to complete it. For example, cutting the samples of the 1018 Steel and 2024 Aluminum. In fact, the experiment helped the group to obtain lots of knowledge about the differences in cutting between Steel and Aluminum. Also, the outsider temperature effects on the sharp, which makes a lot of differences when it comes to cutting such as, the room temperature, dry ice/acetone, antifreeze/water mix with some dry ice, ice/pure water, and boiling water. Last but not least, after those tests the group figured out the differences between the cold and the hot sharps for the Aluminum and Steel. From this experience our group learned more information about materials that will help us when it comes to real life’s work. It gave us the opportunity to know how the outsider temperatures could affect the sharps. The Charpy impact test is a standardized high strain-rate test which determines the amount of energy absorbed by a material during fracture. This absorbed energy is a measure of a given material's notch toughness and acts as a tool to study temperature-dependent ductile-brittle transition.