THE IMPACT-WAVE METHOD TO DETECT A GRIFFITH CRACK AT THE INTERFACE OF COATED MATERIALS

Corrosive-erosive effect on AISI D3 steel, 304 stainless steel and CrN/AlN coating in aqueous NaCl slurries was studied. CrN/AlN multilayer films with a thickness of 3 µm and bilayer period of Λ = 60 nm (50 bilayers) were obtained by using the physical vapor deposition (PVD) technique (magnetron sputtering). The corrosion-erosion experiments were performed in a test machine in which the impingement velocity, impact angle, concentration of solids and pH of the solution were controlled. Polarization curves were simultaneously obtained to correlate the electrochemical effects to the erosive wear mechanisms. The slurry used consists of silica particles suspended in a mixture of acid solution and 3.5% NaCl, with a pH value of 5.6. Electrochemical results showed the best corrosion resistance for 304 stainless steels. Additionally, the surface analysis by SEM micrograph revealed formation of cracks in CrN/AlN multilayers coating and plastic deformation in both steel substrates (AISI D3 steel, 304 stainless steel), especially when the mean impact angle is a critical value of 90°. Measurements of critical and passive current densities showed that the behavior of coated materials differed depending on the substrate that is used. Nonetheless, in a general way, by increasing the impact angle and by changing its incidence from normal to grazing, it led to a resistance to corrosion-erosion processes.

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Simulation and Analysis of Anti-Explosion Capability for Coal Mine Refuge Chamber

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.941-944.2547 ◽

2014 ◽

Vol 941-944 ◽

pp. 2547-2552

Author(s):

Yuan Yuan Zhou ◽

Jun Lin Wan ◽

Ya Wei Zhao ◽

Qin Jian Mao

Keyword(s):

Numerical Simulation ◽

Finite Element Analysis ◽

Maximum Stress ◽

Transient Dynamics ◽

Gas Explosion ◽

Experiment Research ◽

Element Analysis ◽

Impact Wave ◽

Simulation Calculation ◽

The Impact

Experiment research aiming at the anti-explosion capability of the refuge chamber is a complex work with high costs. By using finite element analysis, however, could avoid this issue and implement the simulation and analysis more effectively. Based on transient dynamics approach, numerical simulation calculation and analysis of the dynamic response of the refuge chamber under the impact caused by gas explosion are presented in this paper. The results indicate that, when the refuge cabin under specified explosion impact wave stress, the maximum stress of the cabin is 370.8MPa,which is under the ultimate strength, and the maximum impact wave deformation of the cabin is 9.43mm, which is under the maximum permissive deformation (20mm), therefore the rigidity and the strength of the cabin both meet the demands. The refuge chamber presented in this paper, which remain the integrity of the cabin and the safety of the structure under specified explosion impact, has good anti-explosion ability, and could implemmet the emergency risk avoiding effectively.

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The effect of the blocking of impact ocean waves by the crevasse-ridden ice shelf

10.5194/egusphere-egu2020-9665 ◽

2020 ◽

Author(s):

Yuri Konovalov

Keyword(s):

Band Gap ◽

Numerical Experiments ◽

Amplitude Spectrum ◽

Ocean Waves ◽

Band Gaps ◽

Elastic Model ◽

Ice Shelf ◽

Impact Wave ◽

Wide Range ◽

The Impact

The propagation of high-frequency elastic-flexural waves through an ice shelf was modeled by a full 3-D elastic model, which also takes into account sub-ice seawater flow. The sea water flow is described by the wave equation. Numerical experiments were undertaken both for an intact ice shelf free of crevasses, which has idealized rectangular geometry, and for a crevasse-ridden ice shelf. The crevasses were modeled as triangle/rectangular notches into the ice shelf. The obtained dispersion spectra (the dispersion curves describing the wavenumber/periodicity relation) are not continuous. The spectra reveal gaps that provide the transition from n-th mode to (n+1)-th mode. These gaps are observed both for an intact ice shelf free of crevasses and for a crevasse-ridden ice shelf. They are aligned with the minimums in the amplitude spectrum. That is the ice shelf essentially blocks the impact wave at this transition. However, the dispersion spectrum obtained for a crevasse-ridden ice shelf, has a qualitatively difference from that obtained for an intact ice shelf free of crevasses. Moreover, the dispersion spectrum obtained for a crevasse-ridden ice shelf reveals the band gap &#8211; the zone there no eigenmodes exist (Freed-Brown and others, 2012). The numerical experiments with the crevasse-ridden ice tongue that is 16 km in longitudinal extent, 0.8km width and 100m thick, were undertaken for a wide range of the periodicities of the incident wave: from 5 s to 250 s. The obtained dispersion spectra reveal two band gaps in this range: the first band gap at about 20 s and the second band gap at about 7 s for 1km spatial periodicity of the crevasses. The width of the band gap significantly increases when the crevasses depth increases too. Respectively, the amplitude spectra reveal significantly increasing area of periodicities/frequencies where the ice shelf blocks the impact wave.ReferencesFreed-Brown, J., Amundson, J., MacAyeal, D., & Zhang, W. (2012). Blocking a wave: Frequency band gaps in ice shelves with periodic crevasses. Annals of Glaciology, 53(60), 85-89. doi:10.3189/2012AoG60A120Konovalov, Y.V. (2019). Ice-shelf vibrations modeled by a full 3-D elastic model. Annals of Glaciology, 1-7. doi:10.1017/aog.2019.9

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Investigations of the effect of (Cr1−x, Alx)N coatings’ micro Structure on Impact Toughness

MRS Proceedings ◽

10.1557/proc-843-t1.2 ◽

2004 ◽

Vol 843 ◽

Cited By ~ 2

Author(s):

K. Bobzin ◽

E. Lugscheider ◽

O. Knotek ◽

M. Maes

Keyword(s):

Wear Resistance ◽

Impact Toughness ◽

Physical Vapor Deposition ◽

Test Methods ◽

Coated Materials ◽

Novel Approach ◽

Deposition Parameters ◽

Impact Tester ◽

The Impact ◽

Load Behavior

ABSTRACTOriginated from the tooling industry, PVD (Physical Vapor Deposition) coating development focused on increasing the wear resistance. Nowadays, a steadily increasing market is evolving by coating machine parts. The requirements that have to be met due to the needs of this new market segment focus on tribological behavior. This means, that the focus of wear resistance is shifted towards properties like coefficient of friction, wetting behavior and the response of coatings towards dynamic loads. For many tribological applications, coatings are exposed to severe alternating loads, which are usually left out in common test methods. The approach of common coating test methods are based on the static behavior of deposited coatings. The impact tester is a testing device with a novel approach to dynamic load behavior of both bulk and coated materials. In this paper, the effect of the coatings' microstructure and Young's modulus on the impact toughness was investigated. A change in microstructure was provoked by changing deposition parameters like aluminum content. In a second stage these coatings were then tested with respect to their response to high alternating loads. For this purpose both load and number of impacts were varied.

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