Calibration of High-Frequency Mechanical Impact Simulation Based on Drop Tests
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JMEPEG https://doi.org/10.1007/s11665-020-04817-7
Calibration of High-Frequency Mechanical Impact Simulation Based on Drop Tests Stefanos Gkatzogiannis, Peter Knoedel, and Thomas Ummenhofer (Submitted October 17, 2019; in revised form January 13, 2020) A series of drop tests was implemented in the present study in order to allow the reproduction of a single impact identical to the high frequency mechanical impact (HFMI) under monitored conditions in the laboratory. Therewith, characterization of the investigated materialÕs mechanical behavior by explicitly considering possible irregularities concerning the present deformation modes would be enabled. Main goal was the determination of the investigated materialÕs dynamic yield stress for various strain rates inside the spectrum of interest, so that the Cowper–Symonds viscous material model would be calibrated for the subsequent HFMI simulation. The values of the dynamic yield stress extracted by the present drop tests show good agreement with other experimental methods regarding the investigated material S355. The introduction of the calibrated material behavior on the present drop tests in the finite element (FE) analysis of HFMI led to reduced preciseness though, in comparison with the FE analysis, which considered high strain rate tensile tests found in literature. A series of conclusions was drawn from both the experimental and numerical investigations, confirming most of the initial expectations. Further work is proposed, in order to clarify an incompatibility met during the numerical investigations. Keywords
FE analysis, high frequency mechanical impact, residual stresses, simulation, strain rate dependency
1. Introduction High frequency mechanical impact (Ref 1) is an efficient mechanical post weld treatment that has been proven to increase significantly, even more than 100%, the fatigue life of welded steel structures. The method, up to the moment, has been thoroughly investigated experimentally (Ref 2-10), etc. Based on these experimental investigations of the last decades, the method has been regulated (Ref 1, 11) for the most widely applied welded connections. Nevertheless, it is a common knowledge that the design codes in order to provide guidance for all relative practical applications and still lie on the safe side are usually quite conservative (see Ref 12 for instance). On the contrary, modeling of HFMI with the finite element (FE) method would enable the investigation of various geometries and materials without the restricting cost of experimental investigations. At the same time, it would allow for the consideration of the HFMI effect in fracture mechanics
This article is an invited submission to JMEP selected from presentations at the Symposium ‘‘Joining and Related Technologies,’’ belonging to the topic ‘‘Processing’’ at the European Congress and Exhibition on Advanced Materials and Processes (EUROMAT 2019), held September 1-5, 2019, in Stockholm, Sweden, and has been expanded from the original presentation. Stefanos Gkatzogiannis, Peter Knoedel, a
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