Charpy Impact Test - ME 220 MECHANICS OF MATERIALS LAB...

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ME 220 – MECHANICS OF MATERIALS LAB Charpy Impact Test Test: August 30 th , 2007 Submitted: September 6 th , 2007 Matthew Olsen Section 3
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Summary The Charpy Impact Test is designed to test a material’s toughness under differing conditions, namely temperature. Three materials (Aluminum, A36 Steel, and 4140 Steel) are each tested at temperatures varying from liquid nitrogen, about -320 °F, to boiling water, roughly 212 °F. After lowering or raising the material temperature, the material is placed in a large machine resembling a large pendulum. The pendulum swings down delivering a very large force over a small area of the material. Toughness is defined as a material’s resistance to fracture. It is measured by the energy absorbed in the impact. This absorbed energy is shown by deformation or fracture. A material that absorbs large amounts of energy upon impact is said to be ductile. The material appears to be bent. Materials that fracture easily or cleanly with little deformation are said to be brittle. This mechanical property is not a constant property, however. Three factors result in changes in toughness. These are: temperature, loading rate, and geometry. High temperatures tend to make metals more ductile, while low temperatures tend to make the materials more brittle. Loading rates also affect how ductile the material can be. The faster the force is applied, the less ductile the material tends to be. And geometry relates simply to the presence of a notch or crack. This test held the loading rate and geometry constant. All samples were loaded very quickly, and all had a notch, opposite and parallel to the site of impact. The only variable was the temperature. All
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Charpy Impact Test - ME 220 MECHANICS OF MATERIALS LAB...

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