COKECAN

COKECAN - Thin Wall Structures Bring your own can! ie Pepsi...

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Thin Wall Structures – Bring your own can! ie Pepsi can lab Background In this lab, the application of a strain gauge to a soda can will be completed by each student. Once applied, the strain gauge will be used to measure the strain difference between an unopened and open can. By using some assumptions and the thin walled pressure vessel theory the original pressure can be determined. Objectives: - Learn strain gauge application - Using circuits developed in strain lap obtain strain difference between cans before and after opening - Determine internal pressure using Hooke’s law and thin-walled pressure vessel theory Pre-Lab In what direction, hoop or axial, will you see larger strain values? (Hint: Look at the derived equations in this document!) What is the criterion for a pressure vessel to be considered thin walled? Derive the strain-pressure relationships and include drawing of the idealized volumes with proper labels. (Hint: Read this entire document). Theory and Discussion: Determination of Stresses in the Soda Can In order to determine the pressure in the can we need to find a relationship between the strain values that we can experimentally measure and the pressure exerted by the carbonation of the soda. In your prelab, you will need to determine the criteria for a pressure vessel to be considered thin walled. By applying this criterion to a soda can you will see it is a thin walled pressure vessel. Additionally, the can is clearly a cylinder so we can model it as a cylindrical pressure vessel. The ends are problematic because they are either thicker due to necessity on the pop top side and complex shape on the bottom of the can. To make things easier we can make the assumption that the ends are spherical to simplify the stress-pressure relationships. With these assumptions we can now model our soda can as a cylindrical pressure vessel with spherical end caps. To determine the stress-pressure relationships we need to assign a coordinate system to the pressure vessel. The logical choice is to align one axis along the long side of the cylinder (longitudinal) with the other being in the hoop direction around the cylinder. This results in the third axis in the radial direction. Since the hoop and longitudinal stresses are the principal stress, we know that there are no shear stresses in these directions.
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This note was uploaded on 12/21/2011 for the course EE 102 taught by Professor Xx during the Spring '11 term at BC.

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COKECAN - Thin Wall Structures Bring your own can! ie Pepsi...

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