COMPUTATIONAL AND EXPERIMENTAL STUDY OF THE FALLING LOAD TEST OF HIGH-STRENGTH PIPE STEEL X100 (K80)

The behavior of samples of the promising pipe steel X100 under dynamic three-point bending is studied. This steel is compared with steel X80 currently used in the gas transmission pipeline engineering. Experimental and calculated mechanical characteristics were obtained for pipe steel X100 produced by JSC “VMZ” using data of the standard tests for laboratory samples and drop-weight tests (DWT). Steel X100 demonstrates higher strength indexes in comparison with steel X80, however, it has lower indexes of plasticity and ductile fracture resistance. High-speed video-recording of the crack propagation in a sample of steel X100 was performed in the drop-weight test. In combination with the sample resistance force dependence on the drop-weight movement distance, such testing provided much more information for studying the metal resistance to ductile fracture and allowed revealing the crack propagation law, estimating the specific dissipation energy during the crack propagation, and verifying the computational model used in DWT. Parameters of the X100 steel strain and fracture model were calibrated. The numerical simulation of the behavior of the X100 steel samples in tests at room temperature was performed. Simulation results satisfactorily agree with data of the tests with regard to such parameters as: the sample resistance force dependence as a function of the drop-weight movement distance; the striker work; strained foils, and macrogeometry of fractures in the tested sample. This results may be used for the development of requirements and conditions of using equipped DWT, as well as for the numerical simulation of full-scale tests of pipes made of steel X100 to predict the pipeline resistance to a propagating ductile crack.