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Unformatted text preview: ME313/513 LABORATORY THINWALLED PRESSURE VESSELSFigures from Mechanics of Materials by Higdon et al. 4th edition, John Wiley and Sons, 1985OBJECTIVE: The objective of this experiment is to determine the pressure inside thin walled pressure vessel, such as a carbonated drink can. BACKGROUND: A pressure vessel is any container that is used to store a liquid or gas at a high pressure. Examples of pressure vessels include propane gas containers, balloons, soda cans, the biscuit dough containers, and aircraft fuselages. The pressure inside the pressure vessel is greater than that on the outside. This results in stresses in the container wall. The container wall stretches in response to the stresses. There are two basic forms of pressure vessels: cylindrical pressure vessels are essentially long cylinders with their ends capped off, and spherical pressure vessels. A pressure vessel that has a wall thickness less than about 1/10 of the diameter of the container is called a thinwalled pressure vessel. We will study the soda can as an example of a thinwalled cylindrical pressure vessel. THEORY: Wall Stresses The two principal stresses that develop in a thinwalled cylindrical pressure vessel are the axial stress σaand the hoop stress σh. The axial and hoop stresses are also called the longitudinal and circumferential stresses, respectively. These stresses are related to the internal pressure in the pressure vessel through the following equations: t2pdt4pdha=σ=σwhere p is the internal pressure, d is the diameter of the cylinder and t is the wall thickness. The hoop stress has twice the magnitude of the axial stress. Electrical Resistance Strain Gauges The resistance of the wire depends upon the length of the wire and its cross sectional area. ALRρ=where ρis the resistivity of the metal. If the length L is increased or the cross sectional area A is decreased, the resistance of the wire increases....
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 Spring '08
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 Wheatstone's Bridge

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