Numerical Analysis of Influence of Roughness of Material Surface on High-Speed Liquid Droplet Impingement

Sasaki, H.; Iga, Yuka

doi:10.1115/1.4043320

Cited by 4 publications

References 17 publications

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Relationship between a non-spherical collapse of a bubble and a stress state inside a wall

Iga

Sasaki

2023

Physics of Fluids

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This study performed a fluid/material coupled numerical simulation of the first stage of non-spherical bubble collapse near a wall and investigated the stress state inside the elastic material of the wall according to the change in stand-off distance g between the bubble and the wall. The relationship between the collapse behavior of the bubble and propagation of stress waves was confirmed for typical collapse modes: pancake-shaped mode at g = -0.3, hemispherical mode at g = 0, microjet mode at 0.3 < g < 1.0, and detaching mode at g > 1.2. The stress influence area, which is an index of material damage, was estimated. At 0.3 < g < 1.0, the stress influence area caused by the microjet is narrow and shallow in the material; in contrast, that by the pressure waves spreads more widely and deeply, especially inside the material. This means that the pressure wave has a larger influence than the microjet on damage to a material even though the maximum value of the equivalent stress is nearly identical between the microjet and pressure wave. Additionally, the depth of the stress influence area at 0.3 < g < 0.5 is larger than that at g = 0, although the volume and the maximum stress are larger at g = 0 than at 0.3 < g < 0.5. This indicates that the case of toroidal bubble rebound attaching to a wall has the potential to cause deeper damage inside a material in comparison with hemispherical bubble collapse.

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Relationship between a non-spherical collapse of a bubble and a stress state inside a wall

Iga

Sasaki

2023

Physics of Fluids

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Numerical analysis of fluid-material coupled method on propagation of pressure and stress waves during non-spherical bubble collapse

Sasaki

Endo

Iga

2021

Transactions of the JSME (In Japanese)

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When analyzing cavitation erosion, it is necessary to grasp the stress state inside a material due to the bubble collapse process. In this study, the behavior of a vapor bubble collapse and the stress distribution inside the material due to the bubble collapse were analyzed by using an in-house fluid/material coupled numerical method. In order to evaluate the stress inside the material, the "stress influence area" is introduced and used for the evaluation of the amount of input stress to the material. For analysis results, the two times of impulsive pressure occur in a first collapse, which is caused by two kinds of mechanism, one is a micro-jet, and the other is pressure waves of rebound of the toroidal bubble. Even though the impulsive pressure on a material surface by the micro-jet is smaller than the pressure waves of rebound, the maximum equivalent stress which is installed inside the material is nearly the same value. Further, even though the maximum equivalent stress generated in the material is almost the same, the "stress influence area" is overwhelmingly large in the case of the pressure waves of the rebound as compared to the micro-jet. Therefore, it indicates that the stress state inside the material cannot be predicted just by the measurement of impulsive pressure on the material surface.

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Analysis of the initial stage of fatigue wear in heterostructure materials under contact cyclic loading

Kudryakov

Варавка

Забияка

et al. 2020

Vestnik Donskogo gosudarstvennogo tehničeskogo universiteta

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Introduction. The process of formation of fatigue defects in metal alloys with different structural morphology is considered. The work objective is to develop a computational tool for determining the moment of the defect nucleation under cyclic loading.Materials and Methods. A physical model is built, calculation expressions are presented. The physical model is based on the theory of dislocations. It is shown that a structure factor is particularly important in the process of fracture nucleus origination under dynamic cyclic loading. Depending on the structure and properties of the material, as well as on the nature of the loads, the critical fatigue defect develops in the form of cracks, pores or micro-crater wear.Research Results. A numerical experiment was performed to determine the moment of nucleation of the critical-size defect in iron-base alloys under the drop hypervelocity impacts. Comparative data of calculations and bench tests for droplet impingement erosion of steels and alloys with the structure of ferrite, austenite, sorbitol and martensite are presented. The efficiency of the nucleation stage during the incubation period of erosive wear of the materials studied was evaluated.Discussion and Conclusions. There are no strict instrumental methods for determining the duration of the nucleation stage; therefore, it is recommended to use the proposed analytical model. In addition, the work performed gave a significant application result, i.e. it showed that the focused design of the material structure can significantly increase the wear resistance.

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Numerical Analysis of Influence of Roughness of Material Surface on High-Speed Liquid Droplet Impingement

Cited by 4 publications

References 17 publications

Relationship between a non-spherical collapse of a bubble and a stress state inside a wall

Relationship between a non-spherical collapse of a bubble and a stress state inside a wall

Numerical analysis of fluid-material coupled method on propagation of pressure and stress waves during non-spherical bubble collapse

Analysis of the initial stage of fatigue wear in heterostructure materials under contact cyclic loading

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