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In This paper dynamic forming limit diagram has been investigated as fracture criteria for St13 steel. In fact, effect of various strain rates has been studied. This fracture criterion is based on the Marciniak-Kuczynski (M-K) theory and Solutions of equations have been obtained by applying the Newton -Raphson method. After solution three forming limit diagrams has been created: independent strain rate, dependent strain rate and dynamic forming limit diagram. Dynamic damage criteria investigates forming limit diagram in every strain rate. It is observed that the forming limit is increased by increasing the strain rate, Also for considering the anisotropic and the elastic-plastic behavior of material, the Hill 1948 yield criterion and the Swift hardening rule are used respectively. Also this paper is concerned with the uniaxial tensile properties and formability of sheet metal in relation to the strain rate effects. In order to verification of the results several experiments have been done with a Drop Hammer which is a high speed impact machine. For comparison between quasi static and dynamic damage criterions, all of the stages of experiment were simulated in finite element software Abaqus and results are compared together.

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The cascaded H-bridge (CHB) converter is one of the viable options for large-scale power conversion. Owing to the increased number of components involved in this topology, converter reliability and fault-tolerant control are important issues. This paper proposes a new short-switch fault protection scheme and a post-fault modulation (PFM) strategy to keep the performance of a CHB converter in a static synchronous series compensator (SSSC) application. The SSSC is a series converter to the transmission line, which controls the power flow in the line. Acting as a series converter, any abnormal action of SSSC can affect the whole line reliability. So following the fast fault detections and protections, remedial actions have to be considered to extend normal operation of the SSSC and, in some cases, derate the system to prevent unexpected shutdowns. The new method of short switch fault protection can eliminate the fault in the proper time, while the novel proposed PFM strategy guarantee the continuation of converter operation. This method is based on the application of increasing dc bus utilization techniques in conjunction with the phase shifted pulse width modulation method, which generates the balanced grid currents. Take the advantages of this method; the converter is able to control the transmission line power flow with the remaining healthy H-bridges. Simulation results validate the effectiveness of the proposed method.