The Mechanical Properties of Materials - Report Example

The mechanical properties of materials is directly associated to the response of the material when it is ed to the mechanical stresses. Material’s mechanical behavior is determined by undertaking a simple tensile test in which either cylindrical or flat specimen of uniform cross-section is pulled until it fractures into separate pieces. The initial cross section area, Ao and corresponding gage length, Lo are measured before undertaking the test and the applied load and gage displacement are perpetually measured throughout the test utilizing computer-based acquisition. Based on the original geometry of the sample, the engineering stress-strain behavior can be easily generated from several mechanical properties namely yield strength and elastic modulus Introduction Tensile testing is one of the most basic tests for engineering and offers valuable information concerning a material and its related properties. The tensile testing laboratory was undertaken utilizing the BlueHill data acquisition software. The samples were in the form of cylinder-shaped in cross section with corresponding decreased gage segment. The decreased gage section ensured that the largest stresses occurred in the gage, and not near the grips of the machine thus preventing strain and fracture of the specimen near or within the grips. The trials of the material were tested and the data collected into an existing Excel spreadsheet. The data was utilized to compute diverse properties of the material such as elastic modulus, yield strength, and ultimate tensile strength (Bakis, pp112-145). The data attained were plotted on the prevailing engineering stress-strain curves to relate the samples. The main purpose of this experiment was to collect information concerning the material that aid in determination of basic mechanical properties. This test serves to identify type of polymer sample through testing of material properties. Formulae: Stress = Load (N)/Area of cross-section (mm2) Tensile modulus, E = tensile stress/extensional strain =σ/ԑ= FLo/Ao∆L Strain = extension/ original length Length reduction (%) = (initial length-original length) %/ original length Method and materials Materials: The material utilized in this study is Ultra High Molecular Weight Polyethylene (UHMWPE). Two samples were utilized. Digital calipers in mm and a sharpie marker were utilized in this experiment. Method: The dimensions of the two samples were measured four times of diverse point to attain average width, average thickness and the length of the material. The BlueHill data acquisition software was commenced and the correct material chosen (Bakis, pp112-145). The load cell was zeroed in order to certify that the underlying software solely measured the tensile weight pragmatic to the prevailing specimen. UHMWPE samples were pulled at a fixed degree of 10mm/min and 100mm/min. The data was collected utilizing the software and loaded into a spreadsheet. At a set value of strain, the software stopped utilizing data from the extensometers, and started collecting the strain information utilizing the position of the moving crosshead (Davis, 45-89). The specimen was removed, and the underlying crosshead was then reorganized to the original location to commence another tensile test. The investigation procedure was reiterated for the reset of the specimens. Analysis of material properties were utilized in computation strain, stress and Compressive modulus stated earlier. Result/analysis The average width and thickness for each sample at specified load are provided in the Table 1. Sample 1 Average Width( mm) 19.58 19.24 19.61 19.88 19.58 Thickness(mm) 2.15 2.18 2.21 2.14 2.17 Length of sample #1= 110mm Sample 2 Average Width( mm) 20.5 20.8 20.3 20.7 20.58 Thickness(mm) 2.19 2.21 2.04 2.16 2.15 Length of sample# 2= 102.82 mm Percentage reduction in length= 110-102.82/100 *100% = 7.18% The Young’s modulus is utilized in prediction of the elongation of the material as long as the stress is less than the corresponding yield strength of the material. Ultimate Tensile strength was 0.8Mpa and Yield Strength was 15 Mpa Discussion Materials exhibit peculiar stiffness and tensile strength important to determination of mechanical property of engineering material. In this experiment, the properties of the materials were examined with the purpose of identifying mechanical properties of Ultra High Molecular Weight Polyethylene polymer and undertaking comparison to the compressive test. These polymers have lofty tensile and compressive strength and modulus weight ratios. The sample recorded yield strength of 0.8MPa and ultimate strength of 15Mpa thus depicting high ductility. Moreover, specimen reduced by 7.18% of its original length The percent reduction of the area and corresponding percent elongation are the main indicators of ductility of the material. A more ductile material will have a relatively greater percent elongation and the material will neck down further, resulting in a bigger reduction in area (Bakis, 112-145). UHMWP has high percent elongation due to the straightening of the polymer chains. Polymer chains did not neck down after they were straightened thus resulting in s relatively smaller percent reduction of area compared to other material. Test results were consistent for every sample of the material as depicted on stress-strain curves. Observation of Ultra High Molecular Weight Polyethylene (UHMWPE) graph depicts that it loses stress as it is stretched. The sample might have fractured partially across the cross section prior to complete failure (Davis, 45-89). Moreover, a void resulted to sudden release of stress. The ultimate tensile strength data was 0.8Mpais consistent to the testing procedure thus effective and repeatable. Conclusion The primary objective of this lab experiment was mainly to explore the behavior of material under tensile force in comparison to compression forces. Reactions of diverse material specimens underneath uniaxial tension depict treasured information on their underlying mechanical and mechanical makeup. Elastic modulus, yield location and definitive stress of UHMWPE were determined in uniaxial tension. The dimension of the region of reduced cross section was conspicuous in width, thickness and gage length. At little forces, the central rejoinder was realignment and corresponding rotation of the test fixture. Conversely, at high forces, deformation of the sample was dominant response. The amount of crysallinity of UHMWPE influences numerous tensile mechanical characteristics namely Youngs modulus, strain-hardening rates, and ultimate tensile properties. Works Cited Bakis, Charles E. Composite Materials: Testing and Design, Fourteenth Volume: [the 14th Astm International Symposium on Composite Materials: Testing and Design, Held March 11 - 12, 2002 in Pittsburgh, Pa]. West Conshohocken, PA: ASTM International, 2003. Print. Davis, J R. Tensile Testing. Materials Park, Ohio: ASM International, 2004. Characterization and Failure Analysis of Plastics. Materials Park, OH: ASM International, 2003. Read More