INTRODUCTION
Tensile testing for metallic materials is classified under the ASTM (American Society for Testing and Materials) designation E8/E8M and described as “tension testing of metallic materials in any form at room temperature” to determine “yield strength, yield point elongation, tensile strength, elongation, and reduction of area” (see Figure 1) [1]. This test is the standard to classify a material’s “strength and ductility under uniaxial tensile stresses” and results can be “useful in comparisons of materials, alloy development, quality control, and design under certain circumstances” [1]. The objective of the lab was to conduct an ASTM tensile test on the assigned material of Aluminum 7075, a “very high strength material used for …show more content…
Four cylindrical samples of 7075 Aluminum were tested using the following procedure. First, the test machine was allowed to warm up as suggested in section 7.1 [1]. While the machine warmed up, the initial diameter of the specimens was measured with a Vernier Caliper so that the cross sectional area could be calculated. After the diameter was determined, markings were “drawn with ink” two inches apart on each sample using the Vernier Caliper (7.2.1) [1]. After the samples were prepared for testing, they were placed into the loading cell. The machine was then zeroed as specified in 7.4.1 and testing began using Control Method B outlined in section 7.6.3.2 [1]. Using this method the sample was subjected to a normal force at an extension rate of 0.2 inches/sec. When the sample reached the yield point, the point at which plastic deformation begins, the Instron Extensometer was removed to ensure that it was not damaged, and the test continued at 0.2 inches/second until the specimen reached its failure point. Upon completion of the test, the after fracture method was used to measure the elongation of the sample (7.11.2.2) [1]. This method involves placing the two pieces of the specimen back together and measuring the separation between the original markings. The percent elongation was then determined with the following …show more content…
The average of the experimental data that was taken and calculated was compared to researched ASM (Aerospace Specification Materials) properties [2]. The percentage for reduction of area was not compared, since it was not found in properties provided by ASM. After comparison of the experimental and standard values, a percent error was calculated. From Table 3 it can be seen that the % elongation value differed by 20.93% from the value provided in ASM material data sheet. Yield strength, UTS and elastic modulus values differed by 7.05%, 3.25% and -1.43% respectively. It can be concluded that there is validity in the hypothesis that the material would exhibit the standard properties of an elastic or Young’s modulus of 10.4 x 106 psi and an Ultimate Tensile Strength (UTS) of 83,000 psi since the variance of these values was only -1.43% and 3.25% respectively. Sources of error that could have caused this variance include the slipping of the extensometer during the experiment and the unknown manufacturer pretreatments of all four material samples. Future experiments should be performed in which the extensometer is monitored more closely and the manufacturer pretreatments are known and are identical for all
Tensile testing for metallic materials is classified under the ASTM (American Society for Testing and Materials) designation E8/E8M and described as “tension testing of metallic materials in any form at room temperature” to determine “yield strength, yield point elongation, tensile strength, elongation, and reduction of area” (see Figure 1) [1]. This test is the standard to classify a material’s “strength and ductility under uniaxial tensile stresses” and results can be “useful in comparisons of materials, alloy development, quality control, and design under certain circumstances” [1]. The objective of the lab was to conduct an ASTM tensile test on the assigned material of Aluminum 7075, a “very high strength material used for …show more content…
Four cylindrical samples of 7075 Aluminum were tested using the following procedure. First, the test machine was allowed to warm up as suggested in section 7.1 [1]. While the machine warmed up, the initial diameter of the specimens was measured with a Vernier Caliper so that the cross sectional area could be calculated. After the diameter was determined, markings were “drawn with ink” two inches apart on each sample using the Vernier Caliper (7.2.1) [1]. After the samples were prepared for testing, they were placed into the loading cell. The machine was then zeroed as specified in 7.4.1 and testing began using Control Method B outlined in section 7.6.3.2 [1]. Using this method the sample was subjected to a normal force at an extension rate of 0.2 inches/sec. When the sample reached the yield point, the point at which plastic deformation begins, the Instron Extensometer was removed to ensure that it was not damaged, and the test continued at 0.2 inches/second until the specimen reached its failure point. Upon completion of the test, the after fracture method was used to measure the elongation of the sample (7.11.2.2) [1]. This method involves placing the two pieces of the specimen back together and measuring the separation between the original markings. The percent elongation was then determined with the following …show more content…
The average of the experimental data that was taken and calculated was compared to researched ASM (Aerospace Specification Materials) properties [2]. The percentage for reduction of area was not compared, since it was not found in properties provided by ASM. After comparison of the experimental and standard values, a percent error was calculated. From Table 3 it can be seen that the % elongation value differed by 20.93% from the value provided in ASM material data sheet. Yield strength, UTS and elastic modulus values differed by 7.05%, 3.25% and -1.43% respectively. It can be concluded that there is validity in the hypothesis that the material would exhibit the standard properties of an elastic or Young’s modulus of 10.4 x 106 psi and an Ultimate Tensile Strength (UTS) of 83,000 psi since the variance of these values was only -1.43% and 3.25% respectively. Sources of error that could have caused this variance include the slipping of the extensometer during the experiment and the unknown manufacturer pretreatments of all four material samples. Future experiments should be performed in which the extensometer is monitored more closely and the manufacturer pretreatments are known and are identical for all