Anisotropy of Fractal Dimensions of Fractures and Loading Curves of Steel Samples During Impact Bending

The aim of this study is to establish the correlation between the impact strength and texture, fractal dimensions of fractures , fractal dimensions  obtained from load-time diagrams  reflecting the applied load (P) dependence on time (τ) during the Charpy impact test of ۲۰K steel at various temperatures as well as the comparison of abovementioned fractal dimensions. The tests were carried out on a vertical impact testing machine with a multi-channel system for high-speed registration of forces and strains, as well as a heating and cooling system for samples in a wide temperature range. The load vs. time (load dependence on time) diagrams were obtained at an impact velocity of  = ۴.۴ m/s at temperatures of -۵۰, +۲۰, + ۵۰°С. The Charpy standard samples of ۲۰K steel (analogue to DIN۱۷۱۷۵, class St۴۵.۸) were cut in various directions out of a ۱۲ mm thick the destroyed tank shell of a distillation column for oil refining. It was established that the behavior of both abovementioned fractal dimensions depending on the cutting direction and test temperature coincides qualitatively. The trend of decreasing in fractal dimension with a more viscous nature of fracture was found. The effect of texture is discussed.

Keywords:

: impact tests , impact toughness , fractal dimension , texture , diagram of load changes depending on time