Approximate Blast Wave Theory and Experimental Data for Shock Trajectories in Linear Explosive-Driven Shock Tubes

Freiwald, D.A.

doi:10.1063/1.1661479

Cited by 53 publications

(18 citation statements)

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“…This is supported by the predictions of a model describing the planar expansion of shockwaves [20,30]. The model suggests that the shockwave velocity should increase with a decrease of the irradiated volume.…”

Section: Article In Presssupporting

confidence: 62%

Time-resolved techniques as probes for the laser ablation process

Hauer

Funk

Lippert

et al. 2005

Optics and Lasers in Engineering

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Laser material processing is an increasing market although many processes are still not yet fully understood. It was repeatedly emphasized that a better understanding of the transient processes can help to improve the understanding of the ablation mechanism. Examples using ns-surface interferometry, ns-shadowgraphy and emission spectroscopy are shown to illustrate how these techniques can be used to obtain new insights in the laser ablation processes.Time-resolved surface interferometry probes the remaining polymer, while ns-shadowgraphy and plasma spectroscopy observe the ablation products. Ns-shadowgraphy can be used for fluences just above the ablation threshold, to the fluences where a plasma is observed, which is probed by emission spectroscopy.Time-resolved ns-surface interferometry of a specially designed triazene polymer reveals that the surface morphology changes and thereby the surface removal occurs only during the laser pulse. Ns-shadowgraphy is used to observe the shockwave and the plume of fragments, which are generated during laser ablation. A comparison of the ablation properties of an energetic polymer at two different wavelengths (1064 and 193 nm) shows that the ejection of non-gaseous fragments (solid or liquid) is only detected after irradiation with 1064 nm. At higher laser fluences, plasma is formed, and the atomic (H), and diatomic species (CN, CH and C 2 ) are identified. r

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Section: Article In Presssupporting

confidence: 62%

Time-resolved techniques as probes for the laser ablation process

Hauer

Funk

Lippert

et al. 2005

Optics and Lasers in Engineering

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show abstract

“…A convenient tool for modeling is also an explosion shock tube with a planar HE charge [13][14][15][16]. Much attention is paid to flows in the shock wave in the near zone of the explosion at distances x 200∆ (∆ is the charge thickness) and at the limiting quasi-acoustic stage of the process.…”

Section: Formulation Of the Problemsmentioning

confidence: 99%

Pulsed Loading of Objects during Intense Expansion of Products of Explosion of Solid Explosives (Review)

Lin

2005

Combust Explos Shock Waves

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Specific features of pulsed loading of objects during intense expansion of explosion products of solid explosives are considered. Parameters of the semi-empirical equation of state of explosion products in the density range that has not been adequately considered are given. Results of experimental investigations of reflection of unsteady shock waves from a rigid wall and their effect on thin targets are summarized. Processes that occur under moderate-intensity dynamic impacts on solid and porous media are described: multiple collisions of solids with rigid targets, shock-induced coalescence of nanodiamonds, and emission effects due to expansion of explosion products into an evacuated volume, air, and inert gas.

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“…Since the shock speeds in the solid materials are significantly faster than those in the surrounding air, the effects of the shock waves through these materials will terminate within the first few nanoseconds. The first analytical solution applies to planar blast waves, which will be the case at the center of the laser irradiation area for a limited propagation radius until the edge effects converge on the center axis [206]. Several assumptions are necessary in this theory, such as one-dimensional, instantaneous transfer of the explosive energy into the product gases, uniform distribution of the compressed atmosphere behind the blast front, and averaging of the explosive product velocity and pressure [206].…”

Section: Introductionmentioning

confidence: 99%

“…The first analytical solution applies to planar blast waves, which will be the case at the center of the laser irradiation area for a limited propagation radius until the edge effects converge on the center axis [206]. Several assumptions are necessary in this theory, such as one-dimensional, instantaneous transfer of the explosive energy into the product gases, uniform distribution of the compressed atmosphere behind the blast front, and averaging of the explosive product velocity and pressure [206]. Applying hydrodynamic conservation laws along with these assumptions allows a solution for the propagation radius with respect to the propagation time,…”

Section: Introductionmentioning

confidence: 99%

Laser Application of Polymers

Lippert

2004

Polymers and Light

150

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Laser ablation of polymers has been studied with designed materials to evaluate the mechanism of ablation and the role of photochemically active groups on the ablation process, and to test possible applications of laser ablation and designed polymers. The incorporation of photochemically active groups lowers the threshold of ablation and allows high-quality structuring without contamination and modification of the remaining surface. The decomposition of the active chromophore takes place during the excitation pulse of the laser and gaseous products are ejected with supersonic velocity. Time-of-flight mass spectrometry reveals that a metastable species is among the products, suggesting that excited electronic states are involved in the ablation process. Experiments with a reference material, i.e., polyimide, for which a photothermal ablation mechanism has been suggested, exhibited pronounced differences. These results strongly suggest that, in case of designed polymers which contain photochemically active groups, a photochemical part in the ablation mechanism cannot be neglected. Various potential applications for laser ablation and the special photopolymers were evaluated and it became clear that the potential of laser ablation and specially designed material is in the field of microstructuring. Laser ablation can be used to fabricate three-dimensional elements, e.g., microoptical elements.Keywords Laser ablation · Ablation mechanism · Photopolymers · Polyimide · Spectroscopy This was not always true, of course. For many years, the laser was viewed as "an answer in search of a question". That is, it was seen as an elegant device, but one with no real useful application outside of fundamental scientific research. In the last two to three decades however, numerous laser applications have moved from the laboratory to the industrial workplace or the commercial market. Lasers are unique energy sources characterized by their spectral purity, spatial and temporal coherence, and high average peak intensity. Each of these characteristics has led to applications that take advantage of these qualities: -Spatial coherence: e.g., remote sensing, range finding and many holographic techniques. -Spectral purity: e.g., atmospheric monitoring based on high-resolution spectroscopies. -and of course the many other applications in communication and storage, e.g., CDs.All of these high-tech applications have come to define everyday life in the late twentieth century. One property of lasers, however, that of high intensity, did not immediately lead to "delicate" applications but rather to those requiring "brute force". That is, the laser was used in applications for removing material or heating. The first realistic applications involved cutting, drilling, and welding, and the laser was little more advanced than a saw, a drill, or a torch. In a humorous vein A.L. Schawlow proposed and demonstrated the first "laser eraser" in 1965 [4], using the different absorptivities of paper and ink to remove the ink without damaging the und...

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Approximate Blast Wave Theory and Experimental Data for Shock Trajectories in Linear Explosive-Driven Shock Tubes

Abstract: An approximate theory is presented for predicting the trajectories of gas shocks driven by solid high explosives in linear shock tubes. Theoretical calculations are compared to results of experiments, where agreement within 10% is found.

Cited by 53 publications

References 10 publications

Time-resolved techniques as probes for the laser ablation process

Time-resolved techniques as probes for the laser ablation process

Pulsed Loading of Objects during Intense Expansion of Products of Explosion of Solid Explosives (Review)

Laser Application of Polymers

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