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

90toughness the material. The test is also used as a method to determine the ductile / brittletransition temperature that occurs in metals.The Charpy impact testing consisted of four different types of Charpy V notchspecimens. Three of these specimen types were machined from eyebars taken from theBell Ford Bridge. These specimen types were the longitudinal notched to the side (LS)type, longitudinal notched to the top (LU) type, and Transverse (T) type. The fourthspecimen type consisted of Charpy V notch specimens that were machined from theround diagonals of the bridge near Delphi, IN. The differences between the charpyspecimen types are explained in more detail in Chapter 3.Figure 4.20 is a plot of the impact energy needed to fracture the charpy impactspecimens versus the test temperature for every specimen type. In the plot, the impactenergy for the LU specimens was the greatest, while the T specimens had the lowestimpact energies. For all impact charpy specimens it was difficult to determine atransition temperature between ductile and brittle failure since there was not a significantchange in Charpy impact energy for any of the temperatures tested. Tables 4.5 and 4.6show the results from the Charpy impact tests for each specimen type.According to AASHTO, Indiana is in a Zone 2 since the lowest anticipatedservice temperature is between 0 and -30 o F. The base metal Charpy V-notchrequirements for fracture critical members for ASTM A36 steel is 25 ft lbs at 40 o F in thiszone. Since the A36 steel has the closest material properties to wrought iron, the Charpyimpact energy values should equal or exceed 25 ft lbs. However, for the orientationtested, only the LU specimens were above this minimum.An additional observation from Figure 4.20 is the extremely low impact energyfor the transverse specimen type. The resulting impact energy of this specimen type wasnever greater than 3 ft lbs. This is extremely dangerous if any cracks are running alongthe direction of rolling, which is due to the fibrous nature of wrought iron. Fortunately,