Lab 1 Tension Test

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Northeastern University *

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2355

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Mechanical Engineering

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Jan 9, 2024

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ME 2356 Laboratory Template 1 Department of Mechanical and Industrial Engineering ME 2356: Laboratory for Mechanics of Materials Tension Testing Submitted by Sydney Rodriguez Date Submitted:10/21/2023 Date Performed: 10/06/2023 Lab Section: 12 Lab TA: Lindsey Young Course Instructor: Marguerite Matherne

ME 2356 Laboratory Template 2 1. Introduction The objective of this phase of the experiment is to gather data concerning the strength of the supplied sample and to examine material of Steel’s attributes in depth. 2. Methods and results 2.1 Instron Procedure In this experiment, an Instron 5582 apparatus is employed to assess compression and tension in a given sample. The machine operates by applying force to the material, recording parameters such as time, displacement, and force. Additionally, an extensometer is utilized, a compact device attached to the sample to precisely calculate minor degrees of strain. Data from both these sources are subsequently employed to generate graphs, thereby providing valuable insights into the characteristics of the sample. Results  Sample material and measurements table Table 1. “Steel” sample. Parameter Initial value Final value Unit Length 101.63 N/A mm Diameter 8.960 5.940 mm Area 63.05 27.71 mm^2  Load vs. displacement plot

ME 2356 Laboratory Template 3  Stress vs. strain plot  Mechanical properties table Table 2. “Steel” mechanical properties. Parameter Value Unit Young’s modulus 2.08e+09 N/m^2 Proportional limit 5.79e+08 Pa Yield strength 1.73e+07 Pa Ultimate strength 6.43e+08 Pa True stress 1.14e+09 Pa Reduction of area 45.9 % Elastic energy density 7.19e+06 J/m^3 Discussion 6. On a stress-strain chart, the region beneath the curve at a specific point represents the strain energy density necessary to subject the material to that point on the curve. As the modulus of resilience encompasses the area under the curve until the yield point, it essentially signifies the strain energy density needed to subject the material to its yield strength. 7. The calculated values closely approximate the reference values; however, it's crucial to acknowledge potential sources of error in this experiment. Firstly, discrepancies may inadvertently arise in the procedure and setup due to human error. Additionally, human error can affect the values calculated, as the selection of data points may vary among individuals. Nonetheless, in general, anyone conducting this experiment should achieve comparable results if using the same material and procedure.

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ME 2356 Laboratory Template 4 2.2 Manual tester Procedure This phase of the experiment closely resembles the initial part, employing a tensile test. However, in this case, the operation is manual rather than being performed with the Instron machine. The sample is securely positioned in the apparatus, and the PASCOCapstone software is configured to capture data as the user applies and removes the load from the sample. Results  Sample material and measurements table Table 3. “Aluminum” sample. Parameter Initial value Unit Length 3.2 cm Diameter 3.33 mm  Load vs. displacement plot

ME 2356 Laboratory Template 5  Stress vs. strain plot  Mechanical properties table Table 4. “Aluminum” mechanical properties. Parameter Value Unit Loading Young’s modulus 1.29e+10 N/m^2 Reloading Young’s modulus 1.30e+09 N/m^2 Yield strength 3.64e+07 Pa Ultimate strength 1.89e+07 Pa Discussion 4. The values in this segment do not closely approximate the reference values, considering there is a higher degree of error compared to the first part of the experiment. Naturally, manual operation of the tensile test introduces some inconsistencies, leading to irregularities in the graph. Similar errors in calculations might also manifest in this phase, as in the first one. With repeated experiments by others they should experience different results closer to the reference values online.

ME 2356 Laboratory Template 6 a. Polariscope Procedure In the final stage of the experiment, two samples of the identical material but with distinct shapes are employed. These samples are situated beneath a loading mechanism that can be adjusted to augment the applied load. Additionally, a polarized light source and polarizer are incorporated, enabling the user to visually assess the stress at various locations within the material and observe disparities between the two samples. Results  3 photos of the first sample  3 photos of the second sample

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ME 2356 Laboratory Template 7 Discussion 3. In the second images of both samples, the regions experiencing the most significant stress are highlighted. In the first sample, it's apparent that the point of contact with the load and the immediate vicinity display the highest stress concentrations. Additionally, there are observable stress wave patterns throughout the sample, a consequence of the concentrated nature of the applied load. For the second sample featuring a hole, it's evident that the areas surrounding the hole exhibit the highest stress levels. This is attributed to the varying cross-sectional area at these specific locations, which differs from the rest of the sample. 4. The polariscope method offers numerous potential applications owing to its straightforward approach to stress observation. For those seeking to assess relative stress and make material comparisons without the need for precise data, this method proves highly effective. A company engaged in product design can readily identify both the strongest and weakest areas within the material by simply peering through the polariscope, facilitating informed decisions on necessary reinforcements.

ME 2356 Laboratory Template 8 3. Appendix: Part 1: %clear file clearvars; clc; %read data filename = 'Lab1_InstronData_Steel.csv' ; T = readtable(filename); %sample properties di = 8.960e-3; ri = di/2; li = 101.63e-3; df = 5.940e-3; rf = df/2; Af = pi*rf^2; Ai = pi*ri^2; %conversions Force = T.Force*9.80665; %Load in N Displace = T.Displacement*10^-3; %Extension in m %stress and strain Stress = Force/Ai; Strain = Displace/li; eStrain = T.Strain1; %youngs modulus F = polyfit(eStrain(5:100), Stress(5:100), 1); E = F(1) %yield strength P = polyfit(Strain(20:170), Stress(20:170), 1); oStress = P(1)*Strain(1:200); oStrain = Strain(1:200)+0.002; %Elastic energy density U = 0.5*Stress(870)*Strain(870) %ultimate strength StrengthUlt = Stress(4050) %true stress at failure TrueStress = Force(5000)/Af %proportional limit PL = [Strain(1100), Stress(1100)]; %plot load vs displacement figure(1)

ME 2356 Laboratory Template 9 plot(Displace*10^3, Force) title( 'Load vs. displacement (steel)' ); xlabel( 'Extension (mm)' ); ylabel( 'Load (N)' ); %plot stress vs strain figure(2) plot(Strain, Stress) hold on plot(eStrain, Stress) hold on plot(oStrain, oStress) hold on plot(PL(1), PL(2), 'r*' ) title( 'Stress vs Strain (steel)' ); xlabel( 'Strain (-)' ); ylabel( 'Stress (Pa)' ); legend( 'Crosshead displacement strain' , 'Extensometer strain' , '0.2% Offset' , 'Proportional limit' , 'Location' , 'southeast' ); Part 2: clearvars; clc; filename = 'lab 1 thur 03 (1).xlsx' ; T = readtable(filename); di = 3.33e-3; ri = di/2; li = 3.2e-2; df = 6.35e-3; rf = df/2; Af = pi*rf^2; Ai = pi*ri^2; Force = T.Force_N_Run_2; Displace = T.Position_m_Run_2; Stress = Force/Ai; Strain = Displace/li; F = polyfit(Strain(15:300), Stress(15:300), 1); E = F(1); F2 = polyfit(Strain(581:640), Stress(581:640), 1); E2 = F2(1); P = polyfit(Strain(15:300), Stress(15:300), 1); oStress = P(1)*Strain(1:425); oStrain = Strain(1:425)+0.002; StrengthUlt = Stress(431)

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ME 2356 Laboratory Template 10 figure(1) plot(Displace, Force) title( 'Load vs. displacement (Aluminum)' ); xlabel( 'Extension (m)' ); ylabel( 'Load (N)' ); figure(2) plot(Strain, Stress) hold on plot(oStrain, oStress) title( 'Stress vs. Strain' );