History of Shock Waves, Explosions and Impact – A Chronological and Biographical Reference, Peter O. K. Krehl

Prümmer, R.

doi:10.1002/prep.200990012

Cited by 9 publications

(8 citation statements)

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“…Consequently, the partially melted powder particles stick to the edges of the fused tracks as spatter particles [25]. In addition, spatter particles could form due to the diving of the molten liquid ahead of the laser spot similar to the movement of a boat through water [50]. As a boat moves through water, bow waves develop in front of the advancing motion of the boat.…”

Section: Spatter Particlesmentioning

confidence: 99%

In situ alloying of Ti10Mo fused tracks and layers via laser powder bed fusion

Dzogbewu

Preez

2022

Manufacturing Rev.

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Optimum process parameters for manufacturing a Ti10Mo alloy for biomedical applications via the laser powder bed fusion (LPBF) process were determined. Fused tracks were produced over a wide range of laser powers and scanning speeds, and layers were fused at varied hatch distances. The samples were analysed for continuity of the fused tracks, melting and distribution of the Mo powder particles in the Ti10Mo alloy layers, surface roughness, homogeneity of Mo in the alloy matrix and microhardness. The analysis revealed that the Mo powder particles melted completely in the alloy matrix with only pockets of Mo concentrations, mostly at the peripheries of the fused tracks due to the pushing effect. Complete melting of Mo in the Ti10Mo alloy matrix was due to the small size (1 μm) of the Mo powder particles used in the current experiment. The addition of Mo enhanced the wetting of the powder bed and prevented a pronounced balling effect. From this study, the parameter sets 150 W, 0.5 m/s and 200 W, 1.0 m/s both at a hatch distance of 80 μm, were obtained as the optimum process parameters. However, the Mo concentrations at the peripheries of the molten pool indicated that further research was required before a ‘completely’ homogenous sample could be manufactured via the LPBF process using elemental powder blends.

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Section: Spatter Particlesmentioning

confidence: 99%

In situ alloying of Ti10Mo fused tracks and layers via laser powder bed fusion

Dzogbewu

Preez

2022

Manufacturing Rev.

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“…They play a dominant role in most mechanical flow problems characterised by high-rate drive. Their existence has been observed in a wide range of scales, from microscopic structures to astronomic events and in the four states of matter (Glass 1974;Krehl 2009;Fortov 2021). A deep understanding of how these sudden compressions form, evolve and interact with the surrounding flow and the shocked medium has been pivotal in the progress of many areas, including aerodynamics, propulsion, detonation science, ballistics, inertial confinement fusion or astrophysics, to name a few.…”

Section: Introductionmentioning

confidence: 99%

On the stability of piston-driven planar shocks

2023

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We present a theoretical and numerical stability analysis for a piston-driven planar shock against two-dimensional perturbations. The results agree with the well-established theory for isolated planar shocks: in the range of $h_c< h<1+2 {\mathcal {M}}_2$ , where $h$ is the D'yakov–Kontorovich (DK) parameter related to the slope of the Rankine–Hugoniot curve, $h_c$ is its critical value corresponding to the onset of the spontaneous acoustic emission (SAE) and ${\mathcal {M}}_2$ is the downstream Mach number, non-decaying oscillations of shock-front ripples occur. The effect of the piston is manifested in the presence of additional frequencies occurring by the reflection of the sonic waves on the piston surface that can reach the shock. An unstable behaviour of the shock perturbation is found to be possible when there is an external excitation source affecting the shock, whose frequency coincides with the self-induced oscillation frequency in the SAE regime, thereby being limited to the range $h_c< h<1+2 {\mathcal {M}}_2$ . An unstable evolution of the shock is also observed for planar shocks restricted to one-dimensional perturbations within the range $1< h<1+2 {\mathcal {M}}_2$ . Both numerical integration of the Euler equations via the method of characteristics and theoretical analysis via Laplace transform are employed to cross-validate the results.

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“…Energetic metal nanoparticles have a wide range of applications in military and commercial fields because of their high energy density, extreme surface area, and reaction degree. [1][2][3][4] Particle collision research is very important for the development of space hypervelocity meteorite and debris protection, 5 weapon design, 6 and cold spraying 7 fields. Microscale research is helpful to understand the mechanism of particle collision reactions in extreme environments and enrich the comprehensive understanding of particle collision reactions.…”

Section: Introductionmentioning

confidence: 99%