Comparison of Specific Properties of Engineering Materials | EGR 250, Lab Reports of Materials science

Download Comparison of Specific Properties of Engineering Materials | EGR 250 and more Lab Reports Materials science in PDF only on Docsity! Comparison of Specific Properties of Engineering Materials by Brad Peirson School of Engineering Grand Valley State University Laboratory Module 5 EGR 250 – Materials Science and Engineering Section 1 Instructor: Dr. P.N. Anyalebechi June 28, 2005 1 Abstract The purpose of this laboratory experiment was to use basic measurements of several different samples of engineering materials and calculate their specific properties. To this end the radius, length and mass of fourteen different specimens were measured. The yield strength, tensile strength and elastic modulus was provided for each material. From this data as well the measured dimensions the specific yield strength, tensile strength and modulus were calculated. The results of these calculations show that in general the metal specimen have the highest density, the ceramic sample had a relatively mid-range density and the polymer materials had the lowest density. Introduction The density of a material can be a crucial factor in determining the material that is best suited for an application [1]. The density can be used to determine the relative weights of materials. This is an extremely important factor to consider if the material in question will be used to construct the frame of an aircraft. A lighter weight material will ultimately translate to greater payload capacity and decreased fuel consumption. A more important aspect of the density of the material is the role it plays in calculating its specific strength. The specific strength is simply the strength-to-weight ratio of the material [1]. The specific strength of a material is given by the tensile or yield strength divided by the density of the material. A material with a high specific strength will be suitable for applications such as aircraft and automobiles. This means that the material has a light weight with the aforementioned benefits, but it also has a high strength. Both of these factors are important in such safety conscious applications. The density, and thus the specific strength, of a material can be calculated a number of different ways. The simplest method is to determine the dimensions of a given material specimen and use an applicable formula to determine the volume of the specimen. The formula for the volume of a cylindrical specimen is given in equation 1, 4 Results Table 2 shows the results of the measurements taken form the 14 specimen and the resulting calculated densities. Figure 1 illustrates the relationship between the densities of the different materials. Figure 1 shows that the metals seem to have the highest density. High-alumina does appear to have a higher density than the 2 aluminum alloys, however. The polymers do appear to be the least dense material. Table 2: Physical measurement of 14 engineering samples Material Diameter (mm) Length (mm) Volume (mm 3 ) Mass (g) Density (g/mm 3 ) Titanium 12.76 15.79 2019.17 8.8 0.00436 AA6061 25.51 21.27 10871.2 28.6 0.00263 AA2024 25.43 20.8 10564.4 29.2 0.00276 Brass 25.44 12.61 6409.72 53.9 0.00841 C1018 19.02 19.37 5503.52 42.7 0.00776 Ductile Cast Iron 27.63 18.73 11230.3 78.0 0.00695 Pure Cu - Hot Rolled 25.43 18.36 9325.14 81.6 0.00875 Nylon 6,6 25.48 49.38 25179.1 28.5 0.00113 Polycarbonate 25.44 45.69 23224.4 27.6 0.00119 Polypropylene 26.84 48.93 27684.1 24.6 0.00089 ABS 25.25 37.85 18953 19.7 0.00104 PVC 25.97 47.23 25018 34.5 0.00138 PTFE 19.51 49.66 14846.1 10.8 0.00073 High-alumina 8.06 350 17857.8 61.5 0.00344 Once the density values for each specimen was calculated the specific properties were calculated using the data in table 1. The specific properties were calculated using equations 3, 4 and 5: 5 ρ σ σ y Sy = (3) ρ σ σ tSt = (4) ρ E ES = (5) where σSy, σSt and ES = specific yield strength, specific tensile strength and specific modulus respectively, σy, σt and E = yield strength, tensile strength and elastic modulus respectively and ρ = density of the material [1]. The results of these calculations are given in table 3. 0 0.002 0.004 0.006 0.008 0.01 T it an iu m A A 6 0 6 1 A A 2 0 2 4 B ra ss C 1 0 1 8 D u ct il e C as t P u re C u - H o t N y lo n 6 ,6 P o ly ca rb o n at e P o ly p ro p y le n e A B S P V C P T F E H ig h -a lu m in a Material D en si ty (g /m m ^ 3 ) Figure 1: Calculated densities of the engineering material specimens The data given in table 3 is illustrated graphically in figure 2. Overall the apparent trends in figure 1 that show the difference in the densities of the three material 6 groups do seem to be present in specific strength plots in figure 2. The only noticeable trend in either of the specific strength plots appears to be in the specific yield strength plot. The polymer materials appear to have slightly higher specific yield strengths than the metals. There is also a visible trend in the specific modulus plot. High-alumina ceramic has the highest specific modulus, the metals appear to have a higher specific modulus than the polymers and the polymers have the lowest specific modulus values of the three groups. Table 3: Specific properties of engineering material specimen Material Specific Yield Strength Specific Tensile Strength Specific Modulus Titanium 39007 55068 23633 AA6061 20906 47134 26228 AA2024 27135 66932 26194 Brass 13438 39600 13081 C1018 38022 50911 26680 Ductile Cast Iron 39738 59607 24332 Pure Cu - Hot Rolled 7885 25141 13142 Nylon 6,6 60960 83489 2377 Polycarbonate 52255 56883 2003 Polypropylene 38375 40738 1519 ABS 43294 2309 PVC 31037 33502 2393 PTFE - 37940 687 High-alumina - 121085 110341 Because the specific properties are ratios they are unit-less values. Table 3 shows the raw data illustrated in figure 2. There are no values for specific yield strength of ABS, PTFE or high-alumina because of their stiffness. The yield strength deals with the point of maximum deformation, but these materials are stiff enough that they do not deform prior to failure at the tensile strength point. 9 Because each of the specimens has a tensile strength, the specific tensile strength and the cost per unit tensile strength were the values used to rank the materials. These rankings are shown in table 4. The two different sets of rankings are quite different from one another. However high-alumina did rank highest on both scales. 0.0000 0.0002 0.0004 0.0006 0.0008 0.0010 0.0012 0.0014 0.0016 0.0018 Ti ta ni um A A 60 61 A A 20 24 B ra ss C 10 18 D uc til e C as t I ro n Pu re C u - H ot R ol le d N yl on 6 ,6 Po ly ca rb on at e Po ly pr op yl en e A BS PV C PT FE H ig h- al um in a Material C o st P e r U n it S tr e n g th tensile yield Figure 3: Cost per unit strength comparison for 14 engineering material specimens The final test of the engineering materials was to compare the measured densities to published density values. Table 5 shows the values being compared for each material. The published values for the densities of the engineering materials are not accepted as standard values. Because of this they were not use to perform any formal discrepancy analysis between the measured and published values. Table 5 does seem to show that the measured densities are relatively close to the published values. This is further illustrated in figure 4. 10 Table 4: Rankings of the 14 specimen based on specific tensile strength and cost per unit tensile strength Material Ranking by Specific Tensile Strength* Ranking by Cost per Unit Tensile Strength^ Titanium 6 14 AA6061 8 8 AA2024 3 9 Brass 11 6 C1018 7 2 Ductile Cast Iron 4 3 Pure Cu - Hot Rolled 14 12 Nylon 6,6 2 7 Polycarbonate 5 10 Polypropylene 10 4 ABS 9 11 PVC 13 5 PTFE 12 13 High-alumina 1 1 * Materials ranked from greatest tensile strength to lowest tensile strength ^ Materials ranked from least cost per unit strength to greatest cost per unit strength Table 5: Calculated density values and published density values for engineering materials [3] Material Calculated Density (g/cm 3 ) Published Density (g/cm 3 ) Titanium 4.3582 4.51 AA6061 2.6308 2.7 AA2024 2.7640 2.78 Brass 8.4091 8.75 C1018 7.7587 7.87 Ductile Cast Iron 6.9455 7.1 Pure Cu - Hot Rolled 8.7505 8.96 Nylon 6,6 1.1319 1.16 Polycarbonate 1.1884 1.17 Polypropylene 0.8886 0.9 ABS 1.0394 1.02 PVC 1.3790 1.45 PTFE 2.0746 2.18 High-alumina 3.4439 3.96 11 0.0000 2.0000 4.0000 6.0000 8.0000 10.0000 T it an iu m A A 6 0 6 1 A A 2 0 2 4 B ra ss C 1 0 1 8 D u ct il e C as t P u re C u - H o t N y lo n 6 ,6 P o ly ca rb o n at e P o ly p ro p y le n e A B S P V C P T F E H ig h -a lu m in a Material D e n si ty ( g /c m 3 ) Calculated Published Figure 4: Comparison of calculated and published density values [3] Discussion Figure 1 shows the overall relationship between the densities of the different materials. For the most part it appeared as if the metals had the highest densities of the materials measured. The only exceptions appear to be the two aluminum samples. They each had a density below the high-alumina ceramic. The polymer materials all had densities well below both the metals and the ceramic. Figure 2 seems to show no discernable difference between the specific tensile strengths of metals and polymers. The difference is in the specific modulus values for each group. Figure 2 shows that the metal samples have higher specific modulus values than the polymers. This means that the metals are less likely to deform under and equal amount of force than the polymers. This would likely be the deciding factor between the two material types in a transportation application. The added stiffness of the metals would mean that a vehicle is more likely to be able to withstand any impact it may encounter. It also means that the vehicle’s structure will not be as likely to deform under normal operating conditions, i.e. lift forces under a wing. Based on this data the best choice for the structure of a transportation vehicle would be a metal. The polymers also appear to have slightly higher specific yield strengths than the metals. This would also