Laboratory_1-1

# Laboratory_1-1 - Laboratory 1 Introduction to Strain...

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Laboratory 1 – Introduction to Strain Measurement Purpose: Strain is an important property of a material that can be measured experimentally. The definition of strain is simply the change in length divide by the original length of a material. The changes in lengths are due to loads that are applied to that specimen. In many cases, the change in length is far less than the original length so it is hard to get an accurate measurement of the strain by actually measuring the length. For this reason, it is essential to use a foil resistant strain gage. A foil resistant strain gage is a long strand of wire folded back on itself many times (LAB HANDOUT). This gage is placed and glued to the portion of the material where the strain is desired. As the specimen is loaded, the gage length changes as does the wire. Voltage is applied to the wire, so a change in the

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resistance can be measured. The change in resistance is proportional to the change in length and can be expressed by the equation: dR/R = K*dL/L o where dR = the change in the resistance of the wire R = the original resistance of the wire dL = the change in the length of the specimen L = the original length o of the specimen K = the gage factor The purpose of this experiment is to use the foil resistant strain gage described to measure the strain in Aluminum. Setup and Procedure: The setup shown below (Figure 1) was the basis for the procedure of this experiment. Figure 1. Experimental setup and desired measurements To begin the experiment the dimensions of the specimen bar were measured. These measurements were taken to give an idea of the size of the specimen bar was in relation to the load that was applied. The bar was then clamped to the edge of a table to make rigid end so the beam would be in equilibrium. The strain gage was placed on the
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## This note was uploaded on 03/19/2008 for the course ME 222 taught by Professor Kwon during the Spring '08 term at Michigan State University.

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Laboratory_1-1 - Laboratory 1 Introduction to Strain...

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