MENG_3331-Group_report_Lab_5_Hardness_Resubmission

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MENG 3331 Material Science Department of Mechanical Engineering Sept. 6, 2023, Statesboro, Georgia, USA Technical Report 2 HARDNESS TESTING Dylan Butler Georgia Southern University Albany, Ga, USA Bryce Cone Georgia Southern University Sparks, GA, USA Scott Rhodes Georgia Southern University Warner Robins, GA, USA Lawrence Almeter Georgia Southern University Dearing, GA, USA A BSTRACT The experiment was conducted to become familiar with the Rockwell Hardness Tester and be able to calculate tensile strength given the results of the test. The Rockwell hardness Tester is a very common tool used for determining hardness since it is a very simple tool to use and requires no experience or certifications to use. In the experiment several materials were given to use which include 1018 steel, two samples of 1045 steel, and cast iron. The Rockwell Hardness Tester is then used to determine the hardness number of each material on the HRB scale. A graph of all scales and their equivalent tensile strength is given in the lab manual. Using the chart, the tensile strength of 1018 steel is 88000 psi, 92000 psi, 94000 psi in three trials. The first bar of 1045 steel measured a tensile of 112000 psi, 115,000 psi, and 115,000 psi in three trials. The second bar of 1045 steel read a tensile strength of 109,000 psi, 113,500 psi, and 107,500 psi in three trials. The final piece of material, cast iron, read a tensile strength of 101,000 psi, 104,500 psi, 109,000 psi in three trials. N OMENCLATURE HRB Rockwell Hardness B Scale Psi pounds per square inch (lb/in 2 ) kgf kilogram force (kg x f) INTRODUCTION The Rockwell Hardness tester was created by Stanley Rockwell and Hugh Rockwell which was a differential depth measurement device aimed at standardizing strength testing of different materials [1]. The differential depth measurement test was first performed by Professor Paul Ludwik in 1908 the idea of applying a conical bit (indenter) with a predetermined load (pre-load) to the face of a clean finished piece of material then adding an additional load (major load) of a standard amount to cause deformation in the specimen, after the deformation was complete the major load would be removed and the difference in the deformation with the major load and without would give a standard measurement of the hardness of materials [1,2]. The purpose of this experiment is to establish standardized values of measurement for the hardness of different materials. The Rockwell test consists of multiple different scales which are all used to measure different types of materials as to not damage the machine when testing. This experiment will be focused on the B scale due to the materials being tested, which consist of 1018, 1045, and Cast Iron. Different scales entail different test parameters such as major load and indenters, in the case of scale B the parameters are a major load of 100 kgf and an indenter tipped with a 1/16” radius tungsten carbide ball [1]. In Eqn 1. The variable (d) corresponds to the depth of penetration after the major load is removed. Mean = Σx N (2) 1 Copyright © 2023 by ASME HRB = 130 - (2.5 x d) (1)

In Eqn 2. The variable x corresponds to measured values and N corresponds to the total number of values. Standard Deviation = √ ❑ (3) In Eqn 3. The variable X corresponds to the values measured, the variable X corresponds to the mean of values measured, and N corresponds to the total number of values. EXPERIMENTAL METHODS To perform the hardness test, a series of steps needs to be followed. Starting with using the vice grip and file to smooth the metal face down. Followed by using the lap wheel grinder to make the face of the metal smooth and flat. Once the subject is prepared, the Rockwell Hardness Tester will need to be tested for calibration. This will be done using a metal with a known hardness and perform the hardness test on trial metal three times. Once the calibration is confirmed, the tester will need to be loaded to 100 kgf. This ensures the scale will be read in HRB. Place the metal subject onto the anvil of the tester and raise it until the 1/16th ballpoint indenter pushes down on the metal and the small arrow on the scale hits the little red dot. This means the minor load is being applied to the metal. Now align the big needle of the scale to align with the B. Push the handle on the side of the tester to the loaded position and now the major and minor loads are being applied. The needle will flicker until it stops; this is when the major load will need to be pulled back to unloaded. The needle will move and once it stops moving this is the number that will need to be recorded as hardness. Record the hardness of the metal used and repeat three times for each sample of metal. From the hardness recorded, a hardness vs tensile strength will be calculated. Figure 1 shows a schematic of the process used to perform the hardness test on the Rockwell Hardness test machine. Figure 1. Schematic Process of Using Rockwell Hardness Test Machine DATA AND R ESULTS Table 1 represents the hardness data collected from testing. Table 2 displays the hardness and tensile strength values for the 1018 steel, 1045 steel, 1045 steel test 2, and cast iron. The average hardness for the 1018 steel was 91.0 HRB which is higher than the standard for cold drawn 1018 steel [4]. The average hardness for the 1045 steel was 98.67 HRB and 97.33 HRB which is slightly higher than the standard for cold drawn 1045 steel [5]. The average hardness for the cast iron was 95.67 HRB which is slightly lower than the standard for Gray Cast Iron [6]. All these discrepancies are due to the fact that the type of forging and heat treatment of the samples are unknown. Table 1. Hardness Data For Measured Samples Table 2. Hardness vs Tensile Strength Data Collected Figures 2, 3, 4, and 5 graphically display the relationship between material hardness and tensile strength. The data is found in Table 2. 2 Copyright © 2023 by ASME Materia l Scal e Trial 1 Tria l 2 Tria l 3 Avg Std 1018 HRB 89.5 91.5 92.0 91.00 1.08 1045 HRB 98.0 99.0 99.0 98.67 0.47 1045 #2 HRB 97.0 98.5 96.5 97.33 0.85 Cast Iron HRB 94.5 95.5 97.0 95.67 1.03 Material Hardness TS (10 3 psi) 1018 89.5 88.0 91.5 92.0 92.0 94.0 1045 98.0 112.0 99.0 115.0 99.0 115.0 1045 97.0 109.0 98.5 113.5 96.5 107.5 Cast Iron 94.5 101.0 95.5 104.5 97.0 109.0

Figure 2. 1018 Steel Hardness vs Tensile Strength Curve Figure 3. 1045 Steel Hardness vs Tensile Strength Curve Figure 4. 1045 Steel #2 Hardness vs Tensile Strength Curve Figure 5. Cast Iron Hardness vs Tensile Curve DISCUSSION The experiment required three trials for each of the materials. The results for the hardness were recorded on the HRB scale and the tensile was calculated to PSI. The results for 1018 hardness were 89.5, 91.5, 92.0 with a standard deviation of 1.08. The tensile strength of the 1018 steel came to 88000 psi, 92000 psi, and 94,000 psi. The first 1045 steel has a hardness of 98.0, 99.0, 99.0 with a standard deviation of .47. The tensile strength calculated for the first bar of 1045 steel was 112000 psi, 115000 psi, and 115000 psi. The second bar of 1045 steel was slightly lower than the first bar with a hardness of 97.0, 98.5, 96.5, with a standard deviation .85. The tensile strength was also lower than the first bar of 1045 with the values being 109000 psi, 113500 psi, and 107500 psi. The final piece of material tested was cast iron. The hardness of cast iron is recorded as 94.5, 95.5, 97.0 with a standard deviation of 1.03. The tensile strength of the cast iron is calculated to 101000 psi, 104500 psi, and 109000 psi. After conducting the experiment, it is discovered that in each of the samples of materials there are small dimples left from the hardness tester. The 1045 steel has a visibly larger dimple compared to the cast iron and the 1018 steel. This is likely due to the larger amount of carbon content found, thus making it a harder and stronger metal. The graphs in figures 2, 3, 4, and 5 show the relationship between tensile and strength to support this reasoning. CONCLUSION After using the Rockwell Hardness Test Machine and performing 12 hardness tests with 3 different kinds of metal, the following calculations could be concluded. The 1018 steel had an average hardness of 91 with a standard deviation of 1.08. The first 1045 steel subject had an average hardness of 98.67 with a standard deviation of 0.47. The second 1045 steel subject had an average hardness of 97.33 and standard deviation of 0.85. The cast iron had an average hardness of 95.67 with a standard deviation of 1.03. Q UESTIONS 1. The Rockwell C scale uses a diamond tip with a 150 kgf major load while the Rockwell B scale uses a 1/16” steel ball tip with 100 kgf major load. 2. The indentations must be at least three diameter lengths apart from each other and from the edge of the sample. 3. The thickness requirement for a Rockwell hardness testing sample is a 0.25in (6.35mm) minimum thickness. Superficial testing is used for testing both small and thin samples. 4. The units for Rockwell Hardness are HRB. The units for Brinell Hardness are BHN (kgf/mm 2 ). The units for Vickers Hardness are HV (kgf/mm 2 ). R EFERENCES [1] “Rockwell Scale.” Wikipedia , Wikimedia Foundation, 28 May 2023, en.wikipedia.org/wiki/Rockwell_scale. [2] “Differential Depth Measurement.” Differential Depth Measurement, Measurement Evaluation , 30 July 2018, www.emcotest.com/en/the-world-of-hardness- testing/hardness-know-how/hardness-testing- 3 Copyright © 2023 by ASME

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technologies/measurement-evaluation/differential- depth-measurement/. [3] Shubber, Ahmed, et al. Schematic process of the Rockwell Hardness Test Machine . 14 Feb. 2018. Developing Educational Simulation for Rockwell HardnessTestMachine , https://cdnintech.com/media/chapter/57381/15123451 23/media/F5.png. Accessed 6 Sept. 2023. [4] Aisi 1018 Steel, Cold Drawn , www.matweb.com/search/datasheet_print.aspx? matguid=3a9cc570fbb24d119f08db22a53e2421. Accessed 6 Sept. 2023. [5] Aisi 1045 Steel, as Cold Drawn, 22-32 Mm (0.875- 1.25 in) Round , www.matweb.com/search/datasheet_print.aspx? matguid=9aa951ba895940159b45c570be74b036. Accessed 6 Sept. 2023. [6] Gray Cast Iron, ASTM a 48 Class 40 , www.matweb.com/search/datasheet_print.aspx? matguid=ec56a89f37f74e2f867a64b0f87f1e9d&n=1. Accessed 6 Sept. 2023. 4 Copyright © 2023 by ASME