Evaluation and Repair of Wrought Iron and - Purdue e-Pubs ...

45With the strain gages attached, the sample was ready to be loaded in the testingmachine. The testing was performed in the Kettelhut Structural Engineering Laboratoryusing a 220-kip MTS servo-hydraulic testing machine. A level was used when placingthe coupon in the grips of the machine. This was done to ensure that the specimen wasvertical and that only tension in one direction would occur in the coupon. A two inchextensometer was then attached to the specimen using very tight and strong elastic bandsin the center two inches of the coupon. Figure 3.14 is a photograph of the specimen afterit had been marked, the strain gages had been applied, the extensometer attached, andplaced in the testing machine grips.The strain gages, extensometer, load cell, and stroke readings were all transferredto a Measurements Group System 5000, Model 5100 data acquisition scanner andcomputer where they were interpreted and recorded using Strain Smart software. Thefunction generator and controller of the MTS testing machine were used to control eitherthe loading rate or the (stroke) crosshead rate, depending on the type of test conducted.For each coupon, two different tests were completed.In the initial test, the specimen was loaded only in the elastic region of the stressstraincurve. In this test, the rate of increase in load being applied was controlled whilethe amount of strain in the specimen was recorded. The readings from the strain gages,extensometer, load cell and stroke LVDT of the MTS machine were recorded during thistest. This test was conducted at a rate of five thousand pounds per minute.The sample was only stressed until 15 ksi or less was reached in the specimen.The reason for such a low stress limit during the initial loading was to ensure that thespecimen was never taken out the elastic region for wrought iron and thus permanentdeformations were never created. Using the strain gages, and load cell readings, thestress-strain elastic linear relationship could be plotted for each sample.