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exp: sample preparation for tensile test

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M
Muhammed Fuad Al-Barznji

This document describes an experiment on tensile testing of materials. It discusses preparing dog-bone shaped samples according to ASTM D638 standards. Tensile testing is done using a Shimadzu tensile testing machine to measure properties like stress and strain. Careful sample preparation and dimensions matching standards are needed to obtain accurate property values from the experiment. The conclusions emphasize getting the right sample dimension values according to standards to determine material properties correctly.

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Faculty of Engineering Petroleum Engineering Department Mechanics of Material Lab. Exp. (Sample Preparation) Prepared by: Ahmad Jalal Hasan Muhammad Fuad Rashid Muhammad Hasan Aziz Supervised by: Dr. Dyar Date of Submit: 01/10/2019

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2 Table of Contents 1.1. Aim.......................................................................................................................................................... 3 1.2. Introduction............................................................................................................................................ 3 1.3. tensile test experiment............................................................................................................................ 3 1.4. Sample Preparation................................................................................................................................ 4 1.5. Tensile Specimens and Testing Machines.............................................................................................. 5 1.6. discussion................................................................................................................................................ 7 1.7. Conclusion .............................................................................................................................................. 8 1.8. References............................................................................................................................................... 8

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3 1.1. Aim This International Standard specifies the method for tensile testing of metallic materials and defines the mechanical properties which can be determined at ambient temperature. 1.2. Introduction ASTM's physical and mechanical testing standards provide guides for the proper procedures employed in the determination of the physical, mechanical, and metallographic properties of certain materials, particularly metals and alloys. Using test methods such as scanning electron microscopy, hole-drilling strain-gage method, semiautomatic and automatic image analysis, and X-ray diffraction, parameters like elastic moduli, impact strength, ductility, hardness, residual stress, and grain size are measured. These physical and mechanical testing standards allow metallurgical laboratories, manufacturers, and other producers and users of metals and alloys to examine and evaluate such materials for strength and quality to ensure safety towards their end-use. The mechanical properties of materials are determined by performing carefully designed laboratory experiments that replicate as nearly as possible the service conditions. In the real life, there are many factors involved in the nature in which loads are applied on a material. The following are some common examples of how these loads might be applied: tensile, compressive and shear, just to name a few. These properties are important in materials selections for mechanical design. Other factors that often complicate the design process include temperature and time factors. 1.3. tensile test experiment The topic of this lab is confined to the tensile property of polymers. Figure 6.1 shows a tensile testing machine, which looks similar to the one used in this lab. This test is a destructive method, in which a specimen of a standard shape and dimensions (prepared according to ASTM D 638: standard test method for tensile properties of plastics) is subjected to an axial load. As shown in Figure 6.1, during a typical

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4 tensile experiment, a dog-bone shaped specimen is gripped at its two ends and is pulled to elongate at a determined rate to its breakpoint; a highly ductile polymer may not reach its breakpoint. The tensile tester used in this lab is manufactured by Shimadzu Corporations (model AJS- It has a maximum load of 100 kN and a variable pulling rate. The setup of the experiment could be changed to accommodate different types of mechanical testing, according to the ASTM standard (e.g. compression test, etc). 1.4. Sample Preparation  The polymer specimens are dog-bone shaped. They were injection molded, and its dimensions were determined according to the ASTMD 638, mentioned earlier in the introduction.  Measure the thickness, width and gage length of polymer samples using a pair Vernier calipers. These dimensions should be approximately the same for each sample. Figure 1 A photograph of a tensile machine (Shimadzu, Autograph AG- 10TC).

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5 1.5. Tensile Specimens and Testing Machines Tensile Specimens. Consider the typical tensile specimen shown in Fig. 2. It has enlarged ends or shoulders for gripping. The important part of the specimen is the gage section. The cross-sectional area of the gage section is reduced relative to that of the remainder of the specimen so that deformation and failure will be localized Figure 2 Typical tensile specimen, showing a reduced gage section and enlarged shoulders. To avoid end effects from the shoulders, the length of the transition region should be at least as great as the diameter, and the total length of the reduced section

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6 in this region. The gage length is the region over which measurements are made and is centered within the reduced section. The distances between the ends of the gage section and the shoulders should be great enough so that the larger ends do not constrain deformation within the gage section, and the gage length should be great relative to its diameter. Otherwise, the stress state will be more complex than simple tension. There are various ways of gripping the specimen. The end may be screwed into a threaded grip, or it may be pinned; butt ends may be used, or the grip section may be held between wedges. There are still other methods. The most important concern in the selection of a gripping method is to ensure that the specimen can be held at the maximum load without slippage or failure in the grip section. Bending should be minimized. Testing Machines. The most common testing machines are universal testers. terials in tension, compression, or bending. Their primary function is to create the stress- strain curve described in the following section in this chapter. Testing machines are either electromechanical or hydraulic. The principal difference is the method by which the load is applied. Electromechanical machines are based on a variable-speed electric motor; a gear reduction system; and one, two, or four screws that move the crosshead up or down. This motion loads the specimen in tension or compression. Crosshead speeds can be changed by changing the speed of the motor. A microprocessor-based closed-loop servo system can be implemented to accurately control the speed of the crosshead. Hydraulic testing machines are based on either a single or dual-acting piston that moves the crosshead up or down. However, most static hydraulic testing machines have a single acting piston or ram. In a manually operated machine, the operator adjusts the orifice of a pressure-compensated needle valve to control the rate of loading. In a closed-loop hydraulic servo system, the needle valve is replaced by an electrically operated servo valve for precise control.

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7 0 Figure 3 Systems for gripping tensile specimens. For round specimens, these include threaded grips (a), serrated wedges (b), and, for butt end specimens, split collars constrained by a solid collar (c). Sheet specimens may be gripped with pins (d) or serr 1.6. discussion the dimension for a lab testing exactly for this experiment should match the standard to test a materials properties according to ASTM (American standard testing materials ) that means the sample should have a specification of some properties for example length and height and thickness and dimeter also the sample must a homogeneous sample and so on , also by observing the experiments test for example test it noted that was a successful experiment and dissipating from bias and errors to the graphs and test results, this due to the sample had a uniforming of properties as mentioned high above.

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8 1.7. Conclusion Finally, I would say the process of preparing a sample for specimen’s physical properties should be done carefully and preparing its dimensions due to standards precisely to get the right values for their properties in graph results. 1.8. References  Matweb.com. (2015). MatWeb - The Online Materials Information Resource.  ASTM Standard C33, 2003  National Council on Radiation Protection and Measurements (NCRP)  American Society of Testing and Materials (ASTM)  Radiological and Environmental Sciences Laboratory (RESL), Idaho Falls, Idaho (Operated by the DOE)  DOE Technical Measurements Center, Grand Junction, CO  Environmental Measurements Laboratory (EML); formerly the Health and Safety Laboratory of the DOE

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exp: sample preparation for tensile test

  • 1. Faculty of Engineering Petroleum Engineering Department Mechanics of Material Lab. Exp. (Sample Preparation) Prepared by: Ahmad Jalal Hasan Muhammad Fuad Rashid Muhammad Hasan Aziz Supervised by: Dr. Dyar Date of Submit: 01/10/2019
  • 2. 2 Table of Contents 1.1. Aim.......................................................................................................................................................... 3 1.2. Introduction............................................................................................................................................ 3 1.3. tensile test experiment............................................................................................................................ 3 1.4. Sample Preparation................................................................................................................................ 4 1.5. Tensile Specimens and Testing Machines.............................................................................................. 5 1.6. discussion................................................................................................................................................ 7 1.7. Conclusion .............................................................................................................................................. 8 1.8. References............................................................................................................................................... 8
  • 3. 3 1.1. Aim This International Standard specifies the method for tensile testing of metallic materials and defines the mechanical properties which can be determined at ambient temperature. 1.2. Introduction ASTM's physical and mechanical testing standards provide guides for the proper procedures employed in the determination of the physical, mechanical, and metallographic properties of certain materials, particularly metals and alloys. Using test methods such as scanning electron microscopy, hole-drilling strain-gage method, semiautomatic and automatic image analysis, and X-ray diffraction, parameters like elastic moduli, impact strength, ductility, hardness, residual stress, and grain size are measured. These physical and mechanical testing standards allow metallurgical laboratories, manufacturers, and other producers and users of metals and alloys to examine and evaluate such materials for strength and quality to ensure safety towards their end-use. The mechanical properties of materials are determined by performing carefully designed laboratory experiments that replicate as nearly as possible the service conditions. In the real life, there are many factors involved in the nature in which loads are applied on a material. The following are some common examples of how these loads might be applied: tensile, compressive and shear, just to name a few. These properties are important in materials selections for mechanical design. Other factors that often complicate the design process include temperature and time factors. 1.3. tensile test experiment The topic of this lab is confined to the tensile property of polymers. Figure 6.1 shows a tensile testing machine, which looks similar to the one used in this lab. This test is a destructive method, in which a specimen of a standard shape and dimensions (prepared according to ASTM D 638: standard test method for tensile properties of plastics) is subjected to an axial load. As shown in Figure 6.1, during a typical
  • 4. 4 tensile experiment, a dog-bone shaped specimen is gripped at its two ends and is pulled to elongate at a determined rate to its breakpoint; a highly ductile polymer may not reach its breakpoint. The tensile tester used in this lab is manufactured by Shimadzu Corporations (model AJS- It has a maximum load of 100 kN and a variable pulling rate. The setup of the experiment could be changed to accommodate different types of mechanical testing, according to the ASTM standard (e.g. compression test, etc). 1.4. Sample Preparation  The polymer specimens are dog-bone shaped. They were injection molded, and its dimensions were determined according to the ASTMD 638, mentioned earlier in the introduction.  Measure the thickness, width and gage length of polymer samples using a pair Vernier calipers. These dimensions should be approximately the same for each sample. Figure 1 A photograph of a tensile machine (Shimadzu, Autograph AG- 10TC).
  • 5. 5 1.5. Tensile Specimens and Testing Machines Tensile Specimens. Consider the typical tensile specimen shown in Fig. 2. It has enlarged ends or shoulders for gripping. The important part of the specimen is the gage section. The cross-sectional area of the gage section is reduced relative to that of the remainder of the specimen so that deformation and failure will be localized Figure 2 Typical tensile specimen, showing a reduced gage section and enlarged shoulders. To avoid end effects from the shoulders, the length of the transition region should be at least as great as the diameter, and the total length of the reduced section
  • 6. 6 in this region. The gage length is the region over which measurements are made and is centered within the reduced section. The distances between the ends of the gage section and the shoulders should be great enough so that the larger ends do not constrain deformation within the gage section, and the gage length should be great relative to its diameter. Otherwise, the stress state will be more complex than simple tension. There are various ways of gripping the specimen. The end may be screwed into a threaded grip, or it may be pinned; butt ends may be used, or the grip section may be held between wedges. There are still other methods. The most important concern in the selection of a gripping method is to ensure that the specimen can be held at the maximum load without slippage or failure in the grip section. Bending should be minimized. Testing Machines. The most common testing machines are universal testers. terials in tension, compression, or bending. Their primary function is to create the stress- strain curve described in the following section in this chapter. Testing machines are either electromechanical or hydraulic. The principal difference is the method by which the load is applied. Electromechanical machines are based on a variable-speed electric motor; a gear reduction system; and one, two, or four screws that move the crosshead up or down. This motion loads the specimen in tension or compression. Crosshead speeds can be changed by changing the speed of the motor. A microprocessor-based closed-loop servo system can be implemented to accurately control the speed of the crosshead. Hydraulic testing machines are based on either a single or dual-acting piston that moves the crosshead up or down. However, most static hydraulic testing machines have a single acting piston or ram. In a manually operated machine, the operator adjusts the orifice of a pressure-compensated needle valve to control the rate of loading. In a closed-loop hydraulic servo system, the needle valve is replaced by an electrically operated servo valve for precise control.
  • 7. 7 0 Figure 3 Systems for gripping tensile specimens. For round specimens, these include threaded grips (a), serrated wedges (b), and, for butt end specimens, split collars constrained by a solid collar (c). Sheet specimens may be gripped with pins (d) or serr 1.6. discussion the dimension for a lab testing exactly for this experiment should match the standard to test a materials properties according to ASTM (American standard testing materials ) that means the sample should have a specification of some properties for example length and height and thickness and dimeter also the sample must a homogeneous sample and so on , also by observing the experiments test for example test it noted that was a successful experiment and dissipating from bias and errors to the graphs and test results, this due to the sample had a uniforming of properties as mentioned high above.
  • 8. 8 1.7. Conclusion Finally, I would say the process of preparing a sample for specimen’s physical properties should be done carefully and preparing its dimensions due to standards precisely to get the right values for their properties in graph results. 1.8. References  Matweb.com. (2015). MatWeb - The Online Materials Information Resource.  ASTM Standard C33, 2003  National Council on Radiation Protection and Measurements (NCRP)  American Society of Testing and Materials (ASTM)  Radiological and Environmental Sciences Laboratory (RESL), Idaho Falls, Idaho (Operated by the DOE)  DOE Technical Measurements Center, Grand Junction, CO  Environmental Measurements Laboratory (EML); formerly the Health and Safety Laboratory of the DOE