MT1010 - Impact testing lab report PDF

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Impact testing lab report...

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MT1010 – ENGINEERING MATERIALS LAB REPORT TITLE The Experiment of The Impact Toughness of Metallic Materials

OBJECTIVES 1) To study the principles of brittle fracture in mild steel 2) To understand the impact toughness of materials with different heat and strengthening treatments 3) To interpret obtained experimental data for the selection of engineering materials

INTRODUCTION The impact test determines the impact toughness, which is a material property of metals, most commonly by measuring the work required to fracture metallic specimen under impact. The impact toughness test of metals provides information on ductile-brittle nature of metallic material upon different temperature. There are two state administered tests named Charpy and Izod, were planned advertisement utilized widely to gauge the effect vitality. For the two tests, the example is broken by a solitary over-burden occasion because of the effect of the pendulum. A stop pointer is utilized to record how far the pendulum swings back up subsequent to cracking the example. The effect sturdiness of a metal is controlled by estimating the vitality consumed in the break of the example. This is essentially gotten by taking note of the stature at which the pendulum is discharged and the tallness to which the pendulum swings after it has struck the example. The tallness of the pendulum times the heaviness of the pendulum delivers the potential vitality and the distinction in potential vitality of the pendulum toward the begin and the finish of the test is equivalent to the assimilated vitality. Since toughness is greatly affected by temperature, a Charpy or Izod test is often repeated numerous times with each specimen tested at a different temperature. This produces a graph of impact toughness for the material as a function of temperature. An impact toughness versus temperature graph for a steel is shown in the image. It can be seen that at low temperatures the material is more brittle and impact toughness is low. At high temperatures the material is more ductile and impact toughness is higher. The transition temperature is the boundary between brittle and ductile behavior and this temperature is often an extremely important consideration in the selection of a material.

Figure 1: Charpy Tester

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Figure 2: Charpy Tough

THEORY Toughness is a property, which is capacity of material to resist fracture, when subjected to impact. That is the energy absorbed during the fracture. The toughness of the material depends on following factors. • • • •

Temperature Alloying composition Heat treatments Strengthening mechanisms

Impact testing involves the sudden and dynamic application of the load. Parts such as shafts, bolts, anvils and dies are examples of items subjected to impact loading. Th machine measures the amount of energy absorbed by the specimen for the rapture in Joules unit. The amount of energy absorbed can give an idea indication of the toughness of a material. It can classify the different types of materials into either brittle or ductile materials. When the temperature is high the toughness of the material will be increases and when the temperature is low the toughness of the material will be lower. This is because Carbon and low allay steel represent Body Center Cubic (BCC) Lattice and exhibit toughness transition temperature ranges either above, at or below room temperature depending on a number of factors. At temperature above the transition temperature, the alloy has substantially better toughness than at lower temperature. A notch is supplies on specimen because it ensures that the specimen will break as a result of impact load to which is subjected without notch many materials would simply bend without breaking, so it would be easier to determine ability energy.

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MATERIALS AND APPARATUS A mild steel specimen which is in the room temperature (Figure 3) A mild steel specimen which is cooled to -37°C A mild steel specimen which is boiled to 150°C A notching device (Figure 4) An impact testing machine (Figure 5)

Figure 3

Figure 5

Figure 4

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PROCEDURE 1) Firstly, a v notch was cut at the middle of the specimen which is in the room temperature by using the notching machine. 2) Then, the scale of the impact testing machine was set to the zero. 3) Next, the pendulum was raised up to the higher potential position and it was locked. 4) Then, the specimen was mounted on the anvil by facing the notch as shown in figure 6. 5) After, the pendulum was released by turning the operation knob. 6) Then, the pendulum was stopped by using the breaking system after the specimen broken 7) Next, the reading of the scale which is show the impact energy was noted. 8) After, the fracture surface was obtained. 9) Then, the next specimen which is in -37°C was mounted on the anvil as per the before. 10) Next, step 3, step 5, step 6, step 7 and step 8 were repeated again. 11) After, the last specimen which is in 150°C was mounted on the anvil as per the before. 12) Finally, step 3, step 5, step 6, step 7 and step 8 were repeated again.

Figure 6

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OBSERVATIONS

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CALCULATIONS

RESULTS Table 1: Impact test results Sample No

Sample details

Notch type

Temperature

1

Mild Steel

V groove

27°C

2

Mild Steel

V groove

3

Mild Steel

V groove

-377°C 150°C

Broken Toughness or reading unbroken

Percent ductility

Broken

17 J

11.33%

Broken

13 J

8.67%

Broken

32 J

21.33%

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DISCUSSION

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CONCLUSION Toughness of a material is an important property of a material. Toughness depends on the amount of energy absorbed by the material. Therefore, the toughness shows variation under different temperatures. The toughness will increase with temperature and when the temperature is low the toughness of the material will decrease. In impact test metallic samples in three different temperatures, is tested by fracturing it. And the toughness reading can be obtained using the scale in terms of Joules. Temperature can change the behavior of steel from brittle to ductile from addition of heat and from ductile to brittle by removing the heat. The amount of energy required to break a ductile material is greater than for brittle material.

REFERENCES Ahmed, M., 2019. Academia. [Online] Available at: https://www.academia.edu/27550833/TITLE_Impact_toughness_of_metallic_materials [Accessed 02 August 2019]. Anon., n.d. NDT Resource Center. [Online] Available at: https://www.ndeed.org/EducationResources/CommunityCollege/Materials/Mechanical/ImpactToughness.htm [Accessed 02 August 2019].

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