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

19The committee completed more than two thousand tests on wrought iron barmaterial from nineteen different manufacturers in the United States. Half of these testswere standard tensile tests where the bar specimens were pulled monolithically andresulted in a determination of the tensile strength and percent elongation of the material.The data from these tests was recorded and analyzed. The average ultimate tensile stress,based on 959 testing specimens, was 53700 psi with a standard deviation of 2680 psi,which was 5% of the average. This shows that there was little variation in the ultimatetensile stress. Figure 2.10 is a plot showing the tensile stresses found from this testing.Besides determining the tensile stress of the wrought iron bars, the yield stresswas also determined, but not accurately, through the use of the “first stretch” method. Inthis method, the yield stress, or elastic limit is determined when the amount of weightapplied to the specimen produced the first perceptible change of form divided by thecross sectional area of the bar. Since the values for determining the yield stress are socoarse it can be presumed that they are not very accurate and most likely higher then theactual yield stress of the wrought iron bars tested. The average yield stress, or elasticlimit, of the bars found from testing was 33,300 psi with a standard deviation of 2,990psi, which was 9% of the average. This shows that there was little variation in the yieldstress values determined. Figure 2.11 is a plot showing the yield stresses found from thistesting.Percent elongation was also observed by Beardslee and his committee formajority of the wrought iron bars. The method in acquiring the percent elongationconsisted of measuring the length of each specimen before and after testing and thendetermining the amount that the specimen had stretched. This amount was then dividedby the original length and the percent elongation was determined. The average percentelongation from the testing completed by the committee was 19.12% with a standarddeviation of 12.19%, which was 32% of the average. This shows that there was