Introduction to Engineering Materials - Lab Report Example

INTRODUCTION TO ENGINEERING MATERIALS Name Institution Instructor Date Contents Experiment 1: 3 Experiment 2: 6 Experiment 3: 10 Experiment 4 15 References 18 Experiment 1: Determination of the Young’s Modulus of Elasticity Introduction All materials behave in an elastic manner whenever they are subjected to loads. This implies that once the load is removed, the material returns to its original length and shape. The test performed various materials to determine the Young’s Modulus of Elasticity also indicate the existence of a linear relationship between the extension and the load. During loading of a material using different weight the development of a plastic zone is experienced which demonstrate the plastic properties of such a material. The Young’s Modulus of Elasticity for a particular material can be obtained by determining the slope of straight line obtained from plotting stress against strain. Aim of the experiment This experiment aimed at determining Young’s modulus of various materials through by recording oscillation time during loading by different weights. Apparatus The following apparatus were used in the experiment: Extensometer Hounsfield Tensometer having a 5 KN beam 18/8 Austenitic Stainless steel 70/30 brass 0.1% plain carbon steel Pure copper Procedure 1. The diameter of all specimens was measured and the value obtained was used in calculating their accurate cross sectional areas in square millimeter. 2. Each of the specimen was them placed in extensometer with a gauge length of 50 mm 3. The collects were connected on the specimen before being fixed into tensometer 4. A hand wheel was used in taking up the slack 5. The extensometer was adjusted as well as the weight on the mercury scale and the light was extinguished 6. The extensometer gauge was moved through five small divisions which led to the lighting of the light 7. The extensometer handle was used in increasing the load to the point where the light got extinguished 8. The recording of the load reading was done and the graph paper indented 9. The above procedure was repeated four times for the different specimens and results tabulated 10. The results were used in the calculation of strain and stress for each specimen 11. The slope of the graph was determined through trigonometry which is equivalent to the Young’s Modulus of Elasticity for that material before contrasting the results with the ones available in published data Results and Discussion The results of extensions verse corresponding forces for different specimens were obtained and tabulated as shown below: Pure Copper (1) (2) (3) 𝞓L F 𝞓L F 𝞓L F 0.01 0.90 0.01 1.00 0.01 1.10 0.02 1.45 0.02 1.55 0.02 1.60 0.03 1.95 0.03 2.00 0.03 2.15 0.04 2.55 0.04 2.55 0.04 2.60 0.05 3.00 0.05 3.00 0.05 3.15 0.06 3.80 0.06 3.80 0.06 3.60 Stainless Steel (1) (2) (3) 𝞓L F 𝞓L F 𝞓L F 0.01 0.90 0.01 0.80 0.01 0.85 0.02 1.85 0.02 1.60 0.02 1.80 0.03 2.50 0.03 2.30 0.03 2.50 0.04 3.20 0.04 3.05 0.04 3.20 0.05 3.90 0.05 3.75 0.05 3.95 0.06 4.50 0.06 4.40 0.06 4.50 Five millimeter Carbon Steel (1) (2) (3) 𝞓L F 𝞓L F 𝞓L F 0.01 0.35 0.01 0.38 0.01 0.25 0.02 1.00 0.02 0.70 0.02 0.75 0.03 1.60 0.03 1.50 0.03 1.50 0.04 2.50 0.04 2.30 0.04 2.25 0.05 3.40 0.05 3.30 0.05 3.10 0.06 4.25 0.06 4.15 0.06 3.50 A critical analysis of the results was carried out in order to establish whether they were falling within the acceptable experimentation variations. It was observed that they outcomes were falling within the normal and acceptable variations. The strength to weight ratios of the samples investigated in this experiment are critical considerations when it comes to structural design of various components. The associated values of relative density and Young’s Modulus of Elasticity for the specimens were obtained and the specific modulus computed at indicated below: Specific Modulus = (Young’s Modulus of Elasticity) / (Relative Density) Experiment 2: Tensile and Hardness Tests Aim of the experiment This experiment was aimed at performing hardness and tensile tests on different plain carbon steel specimens to investigate the role of heat treatment and carbon on the tensile strength of a material Apparatus Tensile testing machine having 50 KN load cell and four specimens of plain carbon steel comprising of the following: 0.1% plain carbon steel normalised 0.2% plain carbon steel normalised 0.4% % plain carbon steel normalised 0.4% plain carbon steel water quenched from 850° C Procedure 1. Each test piece was first cleaned using emery cloth and its diameter measured before calculating its area of cross section 2. The elongation gauge was adjusted to five times the diameter of the specimen then to zero 3. Each of the specimens was then placed in the machine and test carried out on it 4. The results from the tests were downloaded using a memory stich and recorded 5. The above procedure was repeated on all other remaining specimens 6. The results obtained were used to calculate the following: Yield stress Fracture stress Proof stress (where it was applicable) Ultimate tensile stress Percentage elongation 7. Three hardness tests were performed on the each specimen and the average harness determined for each specimen Results and Discussion The differences in mechanical properties of the specimens tested results from different levels of strains as well as a complex combination of elastic and deformation behavior. Further, the differences imply that the hardness property of a material is not an intrinsic one. Heat-treated specimen exhibited different mechanical properties during the testing performed since the effect of normalising on their microstructure involved changes in oxide distribution and grain size. In most case, the properties and quality of materials are enhanced through heat treatment processes. Calculation of the approximate ration of yield stress to fracture Graph of extension against force This calculated from the graph as: Approximate ration of yield stress to fracture = (9000-8000) / (4-2) = 1:500 Graphical presentation: Graph of hardness against carbon content with error bars The results obtained from the above graphical presentations demonstrate the existence of experimental and interpretations errors Microscopic view: Sketch of microscopic view of 0.4% plain carbon steel Work hardening refers to the application of plastic deformation process to a material in order to strengthen it. is the strengthening of a metal by plastic deformation. This process of strengthening happens due to dislocation generation and movements around the crystal structure of a given material. Experiment 3: Microscopic examination of materials Aim of the experiment The experiment was aimed at carrying out a microscopic examination different ferrous and non-ferrous metals after undergoing various processes Apparatus 1) A microscope with magnification variability for capturing images 2) Memory stick 3) Etched specimens prepared as follows: 1 A, 0.2% plain carbon steel normalised at 860 °C 1 B, 0.4% plain carbon steel normalised at 860 °C 1 C, 0.8% plain carbon steel normalised at 860 °C 1 D, 0.54% plain carbon steel, Quenched at 840 °C then tempered at 500 °C 1 E, 60/40 Brass, Annealed 1 F, Aluminium alloy (HE 15), Annealed at 380 °C Metallurgical structure: 0.2% plain carbon steel normalised at 860 °C 0.4% plain carbon steel normalised at 860 °C 0.8% plain carbon steel normalised at 860 °C Equilibrium diagram for the specimens A description of the metallurgical structure of each specimen with the appropriate equilibrium diagram Difference between Hypo-eutectoid and Hypereutectoid steel: Hypo-eutectoid steel is one, which contains a carbon percentage of below 0.8% in its composition. It is consists of alpha ferrite and pearlite. Hyper-eutectoid steel has a carbon percentage by composition ranging from 0.8% and 2% and it consists of cementite and pearlite. Figure 1: Fe-Fe3C phase diagram Cementite, Alpha ferrite and Pearlite are three microstructures found in the solution of Fe-C. The formation of the three microstructures takes place through the cooling of austenite. Pearlite comprises of a two-phased structure of lamellar acquired through the alteration of layers of Alpha ferrite and cementite (Cardarelli, 2008). The structure present in the above alloy is metallographic structure. CCT diagram for the water quenched Aluminium alloy specimen Differences between Brasses classified as Cold Working and Hot Working. Brasses classified as cod working are those that demonstrate an increased hardness. They are also known as alpha brasses Since the hardness has a direct proportionality to the yield stress of brass specimen, the yield stress is also increases with an increase in the extent of cold work. Brasses classified as hot working are also referred to as duplex brasses. According to the ideal equilibrium diagram, this category of brass contains zinc proportion of about 38% and 42% and has limited abilities to undergo deformations at room temperature (Davis, 2001). Brass equilibrium diagram Differences between the microstructure of sample 1C and 1F The microstructure of sample 1C indicates the existence of recrystallized grain within areas that are yet to undergo recrystallization. On the other hand, the microstructure of sample 1 F shows evidence of high-energy recrystallization. Alloy composition for Aluminium HE15 3.5 – 4.5 Cu % 0.3 – 0.7 Mg % 0.6 – 0.8 Si % 0.4 – 1.1 Mn % 0.6 max. Fe % Remainder Al % Main mechanical properties Good Hard capability when anodising Easy to plate Plated High levels of strength after heat treatment Industrial applications Used in high strength structural components such as aircraft Used in manufacture of weapons Other structural applications Experiment 4 Using an electron scanning microscope Aim of the experiment This experiment was aimed at using an electron scanning microscope to obtain the images of the cross-sections belonging to the samples subjected to tensile tests and comparing the outcomes with those obtained from an optical microscope Apparatus Optical microscope Electron scanning microscope Memory stick (This was provided by the students) 60 / 40 Brass (60% Copper and 40% Zinc), hot working brass Image from the optical microscope: Example of image with 150 magnifications Image from the Electron scanning microscope: Example of image with 1000 magnification Comparison of image from the two different microscopes: Advantages of Electron microscopes over optical microscopes Higher resolution which allows for higher magnification of about two million times (Schlesinger and Paunović, 2011) Allows for clearer visualization of microstructures Possibility of having a three dimensional view of a specimen being scanned Disadvantages of optical microscopes over Electron microscopes Optical microscope only shows magnification of about 1000 to 2000 times Certain micro-details may not be clear Have lower depth of field compared to Electron scanning microscope Aspects that ESM offers in higher magnifications: Higher resolutions of up to 2 million times Clarity of microstructures Highest magnification Potential issues with the observation when higher magnifications are used: Low glares and contrast making it difficult to view certain details of the sample Lack of complex adjustment during optimized imaging Very high resolutions make it difficult to view an entire or a large sample References Cardarelli, F. (2008). Materials handbook: a concise desktop reference. London, Springer. Davis, J. R. (2001). Copper and copper alloys. Materials Park, Ohio, ASM International. Schlesinger, M., & Paunović, M. (2011). Modern Electroplating. New York, NY, John Wiley & Sons. Read More

60 Stainless Steel (1) (2) (3) 𝞓L F 𝞓L F 𝞓L F 0.01 0.90 0.01 0.80 0.01 0.85 0.02 1.85 0.02 1.60 0.02 1.80 0.03 2.50 0.03 2.30 0.03 2.50 0.04 3.20 0.04 3.05 0.04 3.20 0.05 3.90 0.05 3.75 0.05 3.95 0.06 4.50 0.06 4.40 0.06 4.50 Five millimeter Carbon Steel (1) (2) (3) 𝞓L F 𝞓L F 𝞓L F 0.01 0.35 0.01 0.38 0.01 0.25 0.02 1.00 0.02 0.70 0.02 0.75 0.03 1.60 0.03 1.50 0.03 1.50 0.04 2.50 0.04 2.30 0.04 2.25 0.05 3.40 0.05 3.30 0.05 3.10 0.06 4.25 0.06 4.15 0.06 3.50 A critical analysis of the results was carried out in order to establish whether they were falling within the acceptable experimentation variations.

It was observed that they outcomes were falling within the normal and acceptable variations. The strength to weight ratios of the samples investigated in this experiment are critical considerations when it comes to structural design of various components. The associated values of relative density and Young’s Modulus of Elasticity for the specimens were obtained and the specific modulus computed at indicated below: Specific Modulus = (Young’s Modulus of Elasticity) / (Relative Density) Experiment 2: Tensile and Hardness Tests Aim of the experiment This experiment was aimed at performing hardness and tensile tests on different plain carbon steel specimens to investigate the role of heat treatment and carbon on the tensile strength of a material Apparatus Tensile testing machine having 50 KN load cell and four specimens of plain carbon steel comprising of the following: 0.

1% plain carbon steel normalised 0.2% plain carbon steel normalised 0.4% % plain carbon steel normalised 0.4% plain carbon steel water quenched from 850° C Procedure 1. Each test piece was first cleaned using emery cloth and its diameter measured before calculating its area of cross section 2. The elongation gauge was adjusted to five times the diameter of the specimen then to zero 3. Each of the specimens was then placed in the machine and test carried out on it 4. The results from the tests were downloaded using a memory stich and recorded 5.

The above procedure was repeated on all other remaining specimens 6. The results obtained were used to calculate the following: Yield stress Fracture stress Proof stress (where it was applicable) Ultimate tensile stress Percentage elongation 7. Three hardness tests were performed on the each specimen and the average harness determined for each specimen Results and Discussion The differences in mechanical properties of the specimens tested results from different levels of strains as well as a complex combination of elastic and deformation behavior.

Further, the differences imply that the hardness property of a material is not an intrinsic one. Heat-treated specimen exhibited different mechanical properties during the testing performed since the effect of normalising on their microstructure involved changes in oxide distribution and grain size. In most case, the properties and quality of materials are enhanced through heat treatment processes. Calculation of the approximate ration of yield stress to fracture Graph of extension against force This calculated from the graph as: Approximate ration of yield stress to fracture = (9000-8000) / (4-2) = 1:500 Graphical presentation: Graph of hardness against carbon content with error bars The results obtained from the above graphical presentations demonstrate the existence of experimental and interpretations errors Microscopic view: Sketch of microscopic view of 0.

4% plain carbon steel Work hardening refers to the application of plastic deformation process to a material in order to strengthen it. is the strengthening of a metal by plastic deformation. This process of strengthening happens due to dislocation generation and movements around the crystal structure of a given material. Experiment 3: Microscopic examination of materials Aim of the experiment The experiment was aimed at carrying out a microscopic examination different ferrous and non-ferrous metals after undergoing various processes Apparatus 1) A microscope with magnification variability for capturing images 2) Memory stick 3) Etched specimens prepared as follows: 1 A, 0.

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