FE Simulation of High Frequency Mechanical Impact (HFMI) Treatment – First Results

Gkatzogiannis, Stefanos; Knoedel, Peter; Ummenhofer, Thomas

doi:10.1002/cepa.1136

Cited by 5 publications

(1 citation statement)

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“…Its plastic behavior was defined according to Hollomon (𝜎 = 1328.8𝜀 0.0624 ), where the Hollomon coefficients were calculated by fitting the 𝜎 vs. 𝜀 curve of the uniaxial tensile test. The MHP head is made of cemented carbide, whose hardness is a lot higher than the workpiece's, so it was defined as an undeformable sphere [26], and its diameter is set to 8mm, equal to the MHP head's diameter. The mass of the MHP head is set to 0.563kg, equivalent to the mass of the plunger.…”

Section: Fe Simulation Setupmentioning

confidence: 99%

Precisely tuning the residual stress anisotropy in machine hammer peening

Liu,

Jin,

Shen

2023

Int J Adv Manuf Technol

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Machine hammer peening (MHP) is a novel surface modification process that can strengthen and smoothen the treated parts in one process, significantly improving their fatigue performance. The strengthening effect is mainly due to the induced highly controllable residual compressive stress on the subsurface. However, the residual compressive stress induced by MHP is usually anisotropic, with the component perpendicular to the feed direction more significant than parallel.The anisotropic residual stress will have an adverse effect if the treated parts are subjected to multiaxial loads, which puts forward high demands to precisely tune such anisotropy. For this purpose, a finite element model with a velocity-based driving mode is first established in this paper, which can simulate the residual stress induced by MHP. The origin of the anisotropy is then revealed by analyzing the evolution of the simulated residual stress. Based on this, methods to precisely tune the residual stress anisotropy are proposed. The residual stress anisotropy can be precisely tuned by optimizing MHP parameters, including the overlap ratio, impact velocity, and MHP path.

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Section: Fe Simulation Setupmentioning

confidence: 99%

Precisely tuning the residual stress anisotropy in machine hammer peening

Liu,

Jin,

Shen

2023

Int J Adv Manuf Technol

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Calibration of High-Frequency Mechanical Impact Simulation Based on Drop Tests

Gkatzogiannis

Knoedel

Ummenhofer

2020

J. of Materi Eng and Perform

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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 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.

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