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

82value may not be very accurate but could lead to an approximate estimate of the tensilestrength.4.4 Tensile Coupon Test Results4.4.1 Resulting Fracture SurfacesAll of the fractures of the historic wrought iron tensile coupon testing weresomewhat brittle in nature. The fractured surfaces were very jagged and uneven. Thesefractured surfaces, as seen in Figure 4.4, clearly show the “grain-like” characteristic ofthe wrought iron. The long deposits of iron silicate, known as slag, separated the ironinto fibers that appear to have torn during testing.Before any of the specimens were about to fail during testing, there was no visiblenecking or any typical pre-failure behavior that is typically found in structural steel.Figure 4.5 shows a typical ductile steel failure for a sample of steel tested with the sameprocedures as the wrought iron. As the photograph demonstrates, the steel failureconsisted of a considerable amount of necking, followed by an inclined failure plane thatis typical of ductile failures.The failure of wrought iron was more brittle in nature than the aforementionedsteel. During tensile testing, a slow tearing or ripping of what could be called the grainsof the wrought iron would start to occur and then the specimen would fail almostinstantaneously. In some cases, a crack would occur at the edge of the specimen in themiddle of testing and would remain until the specimen failed in a different area afterundergoing a considerable amount of strain. Figure 4.6 shows a typical failure of awrought iron tensile test coupon immediately after it occurred.