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CE 3410Mechanics of Materials LabLouisiana State UniversityLaboratory Report No. 1Hardness TestbyJoshua Board

Table of ContentsPurpose:............................................................................................................................... 3Introduction: ........................................................................................................................ 3Apparatus and Test Procedures:.......................................................................................... 7Results:.............................................................................................................................. 11Discussion: ........................................................................................................................ 13Sample Calculations: ........................................................................................................ 17Brinell Hardness Test.................................................................................................... 17Rockwell Hardness Test ............................................................................................... 18Conclusion: ....................................................................................................................... 19References......................................................................................................................... 20Appendix ........................................................................................................................... 21Appendices A1 Original Test Data Sheet .................................................................. 21Appendix A2 Material Properties of Steel................................................................. 22Appendix A3 Material Properties of Aluminum ....................................................... 23TABLE OF FIGURESFIGURE 1 - BRINELL HARDNESS TESTER MODEL HB3000B ......................................................................................... 7FIGURE 2 - ROCKWELL HARDNESS TESTER MODEL C504 ............................................................................................ 7FIGURE 3 - RELATIONSHIP BETWEEN BRINELL EXPERIMENTAL HARDNESS AND REFERENCE HARDNESS................................ 13FIGURE 4 - RELATIONSHIP BETWEEN ROCKWELL EXPERIMENTAL HARDNESS AND REFERENCE HARDNESS ............................ 14FIGURE 5 - COMPARISON OF TENSILE STRENGTH BASED ON BRINELL, ROCKWELL, AND REFERENCE DATA............................ 15TABLE 1- BRINELL STANDARDS FOR LOAD, TIME, AND HARDNESS ................................................................................. 4TABLE 2 - RELATIONSH I P BETWEEN HARDNESS NUMBERS AND TENSILE STRENGTH........................................................... 6TABLE 3 - BRINELL HARDNESS TEST DATA AND RESULTS ............................................................................................ 11TABLE 4 - ROCKWELL HARDNESS TEST DATA AND RESULTS......................................................................................... 12

Purpose:The purpose of this laboratory is to determine the hardness and the tensilestrength of three metal samples: 1020 Steel, 6061 Aluminum and 2024 Aluminum. TheBrinell and Rockwell Hardness Tests are used to determine this. With the results obtainedfrom each sample, the engineer will be able to determine how the samples relate to eachother. Both the Brinell and Rockwell Hardness Test are considered to be non-destructive.Introduction:Hardness is the resistance of a material to penetration or abrasion under a locallyapplied load (Ref. 1). We use the concept of hardness almost every day. Any time we fileour nails with a nail file or scratch a CD with our finger nails, hardness is involved.Hardness is used to measure a variety of resistances including: scratching, cutting, andindenting (Ref. 2). Also, Hardness may be used for grading similar materials, checking orcontrolling quality level and controlling uniformity of tensile strength (Ref. 2).As engineers, we find hardness tests useful for estimating the tensile strength ofmaterials. The Brinell and Rockwell Tests are the most common experiments todetermine the hardness of metals. Both Tests measure the resistance to indentation of ametal under a static load. However, as the technology has increased the usage of veryhard steels, very thin materials, very small sized parts, etc, a number of other hardnesstests have developed, and not just for metals but for wood, rubber, plastic, and pavingmaterials (Ref. 2).

The Brinell Test procedures and specifications can be found in ASTM E10. Thetest consists of applying a load through a steel ball with a 10-millimeter diameter for aspecific period of time. The standard for load amount, time period and hardness is shownbelow in Table I.Table 1- Brinell Standards for Load, Time, and HardnessIf the sample is expected to have a Brinell Hardness Number (BHN) greater than 450, anindenter made of a harder material should be used (Ref. 2). After removing the load, anindentation is left on the metal sample. By measuring the diameter of the indentation andusing the known diameter of the steel ball that applies the load, the spherical area iscalculated. The Brinell Hardness Number (BHN) is the ratio of the applied load inkilograms to the spherical area of the indentation in mm (Ref. 1). In order to find the2BHN, the following equation is used: Equation (1)Where:D = diameter of the steel ball, mmd = diameter of the indentationP = load, kg

The Brinell Hardness Number is used to give an estimation of the tensile strength of themetal using the following equation:T.S. = 500 x BHNEquation (2)Where:T.S. = tensile strength, psiBHN = Brinell Hardness NumberThe Rockwell Test procedures and specifications can be found in ASTM E18.This test uses the depth of indentation to determine the hardness number (Ref. 1). Aminor load is applied to hold the sample in place then a major load is applied to indentthe sample. The Rockwell Test is similar to the Brinell Test because both use indentationof a samples surface to determine hardness; however, the Rockwell Test measures depthof indentation not diameter as in the Brinell Test. The Rockwell Test uses smaller loadsand creates smaller indentations on the sample as well (Ref.2). Also the RockwellHardness Tester has a gauge on the machine that will display the Rockwell HardnessNumber, RHN, after the load is removed.For this test, a variety of indenters are used including: steel balls ranging from1/ -inch to -inch and spheroconical diamond tips (Ref.1). There are three standard16loads of 60, 100, and 150 kilograms that can be applied to a sample. Diamond tips alongwith a load of 150 kg are used for hard steel, while steel balls and a load of 100 kg is usedfor softer steel and aluminum. The gauge on the machine has two sets of numbers, a redand a black. 30 hardness numbers offset the scales with the black scale being the lower ofthe two (Ref.2). Each scale also provides a different pre-fix to be recorded with thehardness number, B for red and C for black. The combination of indenter and applied

load leads to what set of numbers, red or black, are used to measure the RockwellHardness Number. A diamond tip with applied load of 150 kg corresponds to the blackscale and a steel ball with 100 kg corresponds to the red scale.The Rockwell Test is used for materials that are beyond the capabilities of theBrinell Test and because the Rockwell Hardness Number is shown on the machine ifreturns faster and more accurate hardness numbers (Ref. 2). However, the Rockwell testdoes not have such an easy way to calculated tensile strength as was afforded to us by theBrinell Test. In order to determine tensile strength, a standardized table showing therelationship between Rockwell Hardness Numbers, tensile strength and other propertieshas been developed and is provided below in Table II.Table 2 - Relationship between Hardness Numbers and Tensile Strength

Apparatus and Test Procedures:Figure 1 - Brinell Hardness Tester Model HB3000BFigure 2 - Rockwell Hardness Tester Model C504 Picturetakenby JoshuaBoard Picturetaken by JoshuaBoard

The Apparatus used for the Brinell Hardness Test is Model HB-3000B, shown inFigure 1. The apparatus used for the Rockwell Hardness Test is Model C504, shown inFigure 2.The Brinell Hardness Test requires the use of the following:1- Brinell Hardness Tester Model HB-3000B (shown in Figure 1)1- Testing Block with known BHN3- Metal test samples1- Microscope of low power1- Ten millimeter diameter steel ballThe Rockwell Hardness Test required the use of the following:1- Rockwell Hardness Tester Model C504 (shown in Figure 2)1- Testing Block with known RHN3- Metal test samples1- 1/16 inch diameter steel ballBoth the Brinell and Rockwell Hardness Tests require three metal cubes with 1-inch sidesto be the test samples. The samples to be tested are 1020 Steel, 6061 Aluminum and 2024Aluminum. Before the test, each sample is inspected for any defects to the surface thatcould affect the results. All three samples were clean and passed inspection.The Brinell Test consists of pressing a steel ball of 10-millimeter diameter intothe test sample for a standard amount of time, which will be 12 seconds for ourlaboratory. The 10-mm steel ball will impose a load of 3000 kg for steel samples and1500 kg for aluminum samples. This load will cause a depression to remain on thesurface of the sample after the load is removed. The spherical area of the indentation can

be calculated from the diameter of the indenter and the diameter of the depression on thesurface of the sample. For the Brinell Test, the steel ball must not deviate in diametermore than 0.01 mm and balls of harder material are to be used if the sample has a knownBHN greater than 450 (Ref. 1). Before starting either test, a test block was used on boththe Brinell and Rockwell testers in order to verify accurate results. Tests should not bemade too close together or too close to the edge of the sample.Procedure for Brinell Hardness Test:1.Verify using the test block that the machine is accurate.2.Determine the proper load to apply to the sample: 3000 kg for steeland 1500 kg for aluminum.3.Set the amount of time for the test. In this lab we will use 12 secondsas our test time.4.Select a test area on the sample, being sure to stay away for the edgesand other indentions made on the sample.5.Turn the screw until the sample and the steel ball contact each otherand continue to turn the screw until the screw slips.6.3XVK 6WDUW WR EHJLQ WKH WHVW DQG FUHDWH DQ LQGHQWDWLRQ RQ WKH VDPSOH.7.Repeat step (4)-(6) two times so that a total of 3 indentations are on thesample.8.Measure the diameter of each indentation with a low powermicroscope.9.Determine the Brinell Hardness Number using Equation (1).

The Rockwell Hardness Test uses a steel ball / -inch in diameter to indent the116surface of a sample. This test uses a smaller load and indenter therefore the indentation issmaller and shallower. Similar to the Brinell test, the hardness number found by theRockwell Test is a function of the indentation on the surface of the sample caused by theindenter under a static load (Ref. 2). However, the Rockwell Test is faster because theRockwell Hardness Number is read straight from the machine. The Rockwell HardnessNumber, RHN, is inversely related to the depth of indentation.Procedure for Rockwell Hardness Test:1.Verify using the test block that the machine is accurate.2.Determine the indenter to use. In this lab we will use a steel ball / -116inch in diameter.3.Select a test area on the sample, being sure to stay away for the edgesand other indentions made on the sample.4.Raise the sample against the indenter by turning the large screw untilthe center gauge is vertical.5.Use the small screw to set the dial reading to zero.6.Press the lever down to start the test.7.Read the RHN from the red scale on the dial and include the prefix%.8.Repeat steps (3)-(7) four times so that a total of five indentations areon the sample.

Results:The Table III below shows the data from the Brinell Hardness Test. Threediameter readings were recorded for each sample. The mean of the results for eachindividual sample is calculated and used as the diameter of the indentation. Knowing theapplied load, the diameter of the indenter and the diameter of the indentation, equation(1)is used to find the Brinell Hardness Number for each sample. Using Equation (2), thetensile strength is determined.Table 3 - Brinell Hardness Test data and results1020Steel2024Aluminum6061AluminumTest No.14.303.904.3024.403.804.3034.403.804.25Mean4.373.834.28BHN19012599.2Tensile Strength (psi)950006250049600Reference BHN*17912095Reference TensileStrength (psi)*870007000045000Brinell Hardness Test Data and ResultsDiameter (mm)Type of Material

Table IV below shows the results of the Rockwell Hardness Test. Five tests werecompleted on each sample and the mean of each sample is calculated. The mean isrecorded and used as the Rockwell Hardness Number, RHN, for each sample. UsingTable II, the tensile strength of each sample is interpolated.Table 4 - Rockwell Hardness Test data and results1020Steel2024Aluminum 6061 AluminumTest No.191.777.758.9293.078.258.6393.079.058.1493.278.959.1593.078.059.0Mean92.878.458.7Tensile Strength (psi)960717175051360Reference RHN**887560Reference TensileStrength (psi)**870007000045000Type of MaterialRockwell Hardness Test Data and ResultsDiameter (mm)

Discussion:Figure 3 below shows a graph of the relationship between the experimental BHNand the reference BHN obtained from MatWeb (Ref. 3), for both the steel and aluminumsamples. The results show only a small deviation from the reference data and it should benoted that 1020 steel showed the most deviation at 5%. Also, each sample out preformedthe reference hardness number recording higher values for hardness. 0204060801001201401601802001020Steel2024Aluminum6061AluminumBrinellHardnessNumber

BHN Ref. BHNFigure 3 - Relationship between Brinell Experimental Hardness and Reference Hardness

Figure 4, shown below, contains a graph of the experimental RHN and thereference hardness numbers given on MatWeb (Ref. 3). Both steel and aluminum samplesremained close to the reference hardness with steel once again being 5% off of reference,but it is interesting to point out that 6061 Aluminum has fallen below the reference dataprovided by MatWeb (Ref. 3). In all other cases the hardness of the samples has exceededthat of the reference hardness. After comparing the data, both the Brinell and Rockwelltest are producing accurate numbers and a maximum deviation of 5% over all furtherbacks up both tests accuracy. 0.010.020.030.040.050.060.070.080.090.0100.01020Steel2024Aluminum6061AluminumRockwellHardnessNumber

RHN Ref. RHNFigure 4 - Relationship between Rockwell Experimental Hardness and Reference Hardness

0200004000060000800001000001200001020Steel2024Aluminum6061AluminumTensileStrength(psi)

Brinell Tensile Strength (psi) Rockwell Tensile Strength (psi)Figure 5 - Comparison of Tensile Strength based on Brinell, Rockwell, and Reference dataFigure 5 above shows a comparison of the tensile strength recorded for eachsample based on the Brinell and Rockwell tests. The graphs show that the Rockwell testrecorded higher tensile strength for each of the samples but both 1020 steel and 6061aluminum were determined to have values that were similar. The sample of 2024Aluminum recorded interesting results as the greatest difference between the Brinellstrength and Rockwell strength was found here. The Brinell test is more accurate forfinding tensile strength, based on Equation (2)V VLPSOLFLW\, ZKHUH WKH 5RFNZHOO WHVW KDVmore room for error when interpolating Table II. For both tests, steel was determined tobe the sample that exceeded the reference values for tensile strength by the most. 6061Aluminum was found by both tests to be harder than the reference values. For 2024

Aluminum, the Rockwell test showed expected results, however the Brinell testdetermined that the 2024 Aluminum was not as strong as the reference tensile strength.Looking through the formulas, it seems that the Brinell Hardness Tests was able to createtoo large of an indentation in the surface of the 2024 Aluminum, recording a diameter of3.83 mm. An indentation closer to 3.63 mm would have given the correct tensile strengthaccording to the reference data.From the results shown it Figures 4, 5 and 6, it is clear that some errors haveoccurred. The Brinell Test required the reading of the diameter through a scope whichcould have lead to inaccuracies due to human error. Also it is possible that the load wasprematurely removed from the sample before the 12 seconds had expired. For theRockwell test it is possible that the numbers on the gauge were incorrectly read.However, there are other sources of error that can be pointed to in this lab. During the setup of the experiment it was noticed that the last inspection of the equipment was in 1999and the label stated that both machines need to be inspected yearly.

Sample Calculations:Brinell Hardness Test(1020 Steel) Brinell Hardness Number, BHND = 10-mmP = 3000 kgd = 4.37-mm BHN = 190Tensile Strength = BHN x 500= 190 x 500= 95000 psi

Rockwell Hardness Test(1020 Steel) Rockwell Hardness Number, RHNRHN = 92.8(Read for gauge on Rockwell Tester)Tensile Strength = 96071(Found using Table II)

Conclusion:The Brinell and Rockwell experiments are two tests that are both designed to testthe hardness of a metal sample. The Brinell test measures the diameter of an indentationin order to obtain a hardness number and the Rockwell test measures the depth ofpenetration and returns a hardness number. Both tests are similar in this way but eachoffered its own individual advantages: Brinell with its ease of calculating tensile strengthand Rockwell with its direct readings of hardness number for the machine. Bothexperiments are also considered non-destructive.Looking at the results it seems that both tests found our samples for the most partto be harder than the reference numbers indicated. The most likely source of errorhowever seems to be the decade between inspections for both machines leading touncertainty in the numbers they are providing. In future tests, more experience with themachine and metal samples along with better maintenance of the equipment would helpto reduce errors. The recorded error for the hardness numbers was less than 5% for boththe Brinell and Rockwell Hardness Tests and therefore each test can be consideredreasonably accurate in terms of the tensile strength of a sample.

References1.Mechanics of Materials Laboratory Manual CE 3410, Department of Civil andEnvironmental Engineering, Spring 2007, pT1-1 T1-10.2.Jacobs, C., CE 3410 Notes +ardness 7HVWLQJ, UHFHLYHG LQ FODVV RQ -DQXDU\ , .3.www.MatWeb.com4.ASTM E 10 Standard Test Method for Brinell Hardness of Metallic Materials, ASTMInternational, April 2001.5.ASTM E 18 Standard Test Method for Rockwell Hardness and Rockwell SuperficialHardness of Metallic Materials, ASTM International, April 2001.

AppendixAppendices A1 Original Test Data SheetBrinell Hardness Test(Diameter, mm)Rockwell Hardness Test(RHN)1020Steel4.3791.793.093.093.293.06061Aluminum4.2858.958.658.159.159.02024Aluminum3.8877.778.279.078.978.0

Appendix A2 Material Properties of Steel Mechanical PropertiesMetricEnglishCommentsHardness, Brinell179179Hardness, Knoop200200Converted from Brinell hardness.Hardness, Rockwell B8888Converted from Brinell hardness.Hardness, Vickers188188Converted from Brinell hardness.Tensile Strength, Ultimate600MPa87000psiTensile Strength, Yield370MPa53700psiElongation at Break23.00%23.00%in 50 mmReduction of Area64.20%64.20%Modulus of Elasticity200GPa29000ksiTypical for steelBulk Modulus140GPa20300ksiTypical for steelPoissons Ratio0.290.29

Appendix A3 Material Properties of Aluminum Mechanical PropertiesMetricEnglishCommentsHardness, Brinell120120AA; Typical; 500 g load; 10 mm ballHardness, Knoop150150Converted from Brinell Hardness ValueHardness, Rockwell A46.846.8Converted from Brinell Hardness ValueHardness, Rockwell B7575Converted from Brinell Hardness ValueHardness, Vickers137137Converted from Brinell Hardness ValueUltimate Tensile Strength483MPa70.0ksiAA; TypicalTensile Yield Strength345MPa50.0ksiAA; TypicalElongation at Break18.00%18.00%AA; Typical; 1/16 in. (1.6 mm) ThicknessModulus of Elasticity73.1GPa10600ksiAA; Typical; Average of tension and compression. Compression modulus is about 2% greater than tensile modulus.Notched Tensile Strength379MPa55000psi2.5cm width x 0.16 cm thick side-notched specimen, K = 17.tUltimate Bearing Strength855MPa124000psiEdge distance/pin diameter = 2.0Bearing Yield Strength524MPa76000psiEdge distance/pin diameter = 2.0Poissons Ratio0.330.33138MPa20000psi@# of Cycles 5.00e+8@# of Cycles 5.00e+8Machinability70.00%70.00%0-100Scale of Aluminum AlloysShear Modulus28.0GPa4060ksiShear Strength283MPa41000psiAA; TypicalFatigue Strengthcompletely reversed stress; RR Moore machine/specimen