Material Lab Report 3

Title: Brinel hardness test

Objectives

The objective of this experiment is to test the hardness of the material

Apparatus

Universal Hardness Tester

Introduction

The Rockwell Hardness test is a hardness measurement based on the net increase in depth of

impression as a load is applied. Hardness numbers have no units and are commonly given in the R, L, M, E and K scales. The higher the number in each of the scales means the harder the material. In real life, we need to test the material so that we can find a suitable material for the product or the project.

Hardness Tester

Procedure

1. Put the test specimen on the test bench

2. Turn the hand wheel in order to place the indentation body until both needles have reached

their marked position

3. The pre-load 10kP = 98.1N is applied

4. In the lower part of the device, set the test duration to 10 second

5. Starts is pushed which causes the main load to be applied. The load light is turned out and

indicates the effectiveness of the main load

6. After the given load time, the specimen is unloaded

7. Read the dial gauge reading and tabulate the result in Table 1

8. Take the specimen out of the device and the indentation is measure with measuring

microscope

9. Repeat the procedure for different material and tabulate the result in Table 1.

Results

Specimen Aluminium Brass Copper Indentator Round Round Round HRB (1) 75 99.5 92.5 HRB (2) 74.8 99.4 90 HRB (3) 75 99.5 97 Mean HRB 74.9 99.5 93.2 Specimen Indentator HRB Average diameter Steel Diamond 99.2/ 99.4/ 97 98.5

Discussion

From the table, we are comparing the hardness of Aluminium, Brass, Copper and Steel. We found that Copper is having the weaker hardness and Aluminium is having the stronger hardness campare with aluminium, brass, and copper.

But we also can say that steel have the strongest hardness compare with the other material because when the indentator to test the steel is diamond, and we know that the diamond is the strongest material in the world.

Conclusion

Hardness is property of a metal, which gives it the ability to resist being permanently, deformed (bent, broken, or have its shape changed), when a load is applied. The greater the hardness of the metal, the greater resistance it has to deformation.

The hardness of a metal limits the ease with which it can be machined, since toughness decreases as hardness increases Toughness is a combination of high strength and medium ductility. Toughness is the ability of a material to resist the start of permanent distortion plus the ability to resist shock or absorb energy.

From the experiment, we found are able to determine the hardness between Aluminum, Brass and Copper. We found that Aluminum is having the stronger hardness among of them where Copper is having the weaker hardness. This may due to the different between their crystal structures.

Title: Behavior of plastic material

Objectives

In this experiment, we need to observe about plastic deformation by using 4 materials.

Background / Supporting Theory

Percent reduction in area: The ductility of a metal or alloys can be expressed in terms of the percent reduction in area. Using the measurements of the initial and final diameters, the percent reduction in area can be determined form the equation below:

% Reduction in area ? Ao-Af(100%) Ao

Where Ao = initial cross sectional area of specimen Af = final cross sectional area of specimen

The percent reduction in area, like the percent elongation, is a measure of the ductility of the metal and is also an index of quality. The percent reduction in area may be decreased if defects such as inclusion and/or porosity are present in the metal specimen.

Procedure

1. Measure the initial diameter of given specimens 2. Position the test specimens in the machine load 3. Load the specimen until it breaks

4. Measure the final diameter of specimen at breaking point 5. Study the fracture of the broken specimens 6. Records the data in Table 1

7. Repeat step 1~5 with different materials

Results Original Final Diamater Diameter % Load Materials (mm) (mm) Ao Af Reduction (kN) Aluminium 5.30 2.75 22.06 5.94 73.08 5.5 Copper 5.20 4.10 21.24 13.20 37.83 6.7 Brass 5.10 4.10 20.43 13.20 35.37 11.1 Steel 5.50 3.10 23.76 7.55 68.23 13.2

Discussion

From the table, we know that Aluminium having the largest % reduction and following with Steel, Copper and Brass.

From the experiment, we can understand that the ductility fracture happens with three conditions:

1. Specimen forms neck and cavities within neck.

2. Cavities form crack and crack propagates towards surface, perpendicular to stress. 3. Direction of crack changes to 450 resulting in cup-cone fracture.

Conclusion

From this experiment, we can understand that the different material may have different tensile failure. To calculate the reduction, we are able to study the plastic deformation between different materials where it can be calculation by below equation:

% Reduction in area ? Ao-Af(100%) Ao

The ductility fracture defined as high plastic deformation and slow crack propagation and it happens as per below:

1. Specimen forms neck and cavities within neck.

2. Cavities form crack and crack propagates towards surface, perpendicular to stress. 3. Direction of crack changes to 450 resulting in cup-cone fracture.

Title: Crack of material under different failure mode

Objectives

In this experiment, we need to observe the different kind of fracture.

Discussion

According to the experiment of fatigue fracture, ductility fracture, and impact fracture, we know that materials under different condition will cause different failure mode which are fatigue fraction, ductility fracture and impact fracture. All of these fracture will happens as per below according to the graphs taken during the experiment:

Fatigue Fracture: Fatigue happen from outside to inside of the diameter (grey colour area) and it

break suddenly when the metal’s cross sectional area too small to withstand applied load (black colour area). This kind of fracture happen when the material is having a vibration with a load applies.

Ductility Fracture: Ductility happen with high plastic deformation and slow crack propagation which

specimen forms neck and cavities within neck, then Cavities form crack and crack propagates towards surface, perpendicular to stress until it break. Direction of the crack changes to 45? and have a cup-corn fracture.

Impact Fracture: the metal can’t withstand the single impact force; as a result, it’ll break into two

pieces.

Conclusion

We can understand that the different kind of fracture will happen in different condition, and we can see the difference by visually. The impact strength of materials, the hardness of materials, the effect of fatigue fracture, and behaviours of plastic material will affect the material. All of this fracture shall consider during the design stage of a product.