ASE 324L - Lab 2 - Tension Tests of Steel

ASE 324L - Lab 2 - Tension Tests of Steel - ASE 324L Lab...

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ASE 324L Lab #2: Tension Test of Steels Purpose : In this lab exercise, tension tests will be performed on both hot rolled and cold rolled 1020 steels with the purpose of demonstrating tension test methods. This will provide experience with the analysis of stress-strain curves as a means of characterizing the mechanical behavior of materials under quasi-static (slowly applied) tensile loads. Background : Rolling is a manufacturing process that produces the variety of commercially available shapes and sizes of steel stock. The process of rolling consists of forcing a billet of steel through a narrow passage between two rolls. As the steel passes through the rolls it is deformed to the shape and size of the passageway (see Figure 1 for illustration). Permanent strain Figure 1: Rolling a billet to produce a sheet of material Often, steel is rolled at a temperature above the annealing temperature; this is termed hot rolling . At this elevated temperature, steel is somewhat malleable and is readily deformed to the desired shape and size. After rolling, the steel recrystallizes as it is cooled and is sold in this condition. As a result, the microscopic crystal structures are not much altered, comparing to the steel before rolling. The strength and hardness of annealed steel can be increased by several methods, one of which is cold working . Cold working consists of imparting a permanent deformation to the steel at a temperature far below the annealing temperature. This deformation affects the microstructure of the steel; more crystalline defects called dislocations are generated and they are forced to move by the stresses applied onto the material. The dislocations tangle with each other and this tangling impedes their further motion. Since dislocation motion is necessary for plastic deformation of the steel, an impediment to their motion results in increased strength and
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2 hardness. The subjects of steel microstructure and deformation mechanisms will be covered in greater detail later on in the course. Procedure: The version of the tension test that we will use is one in which the displacement is applied to the specimen grips at a constant rate (ramp loading). That is, the displacement (and, in this case, strain) on the specimen is increased at a constant rate until the specimen fractures while simultaneous measurements of the stress and strain levels are made. In order to accomplish this test, we use a screw driven loading device to provide the displacement control. Make the following measurements of your specimen: specimen diameter and gage length. With the marking pencil that will be provided, mark the gage length on the sample. Be sure to record this data. We will conduct a tensile test on each material, hot-rolled steel (HRS) and cold-rolled
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This note was uploaded on 09/18/2011 for the course ASE 324L taught by Professor Leichti during the Spring '08 term at University of Texas at Austin.

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ASE 324L - Lab 2 - Tension Tests of Steel - ASE 324L Lab...

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