Shock wave

About: Shock wave is a research topic. Over the lifetime, 36184 publications have been published within this topic receiving 635848 citations. The topic is also known as: Shock waves & shockwave.

FEM calculation of residual stresses induced by laser shock processing in stainless steels

Abstract: Laser shock processing, also known as laser shock peening, generates through a laser-induced plasma, plastic deformation and compressive residual stresses in materials for improved fatigue or stress corrosion cracking resistances. The calculation of mechanical effects is rather complex, due to the severity of the pressure loading imparted in a very short time period (in the ns regime). This produces very high strain rates (106 s−1), which necessitate a precise determination of dynamic properties.Finite element techniques have been applied to predict the residual stress fields induced in two different stainless steels, combining shock wave hydrodynamics and strain rate dependent mechanical behaviour. The predicted residual stress fields for single or multiple laser processes were correlated with those from experimental data, with a specific focus on the influence of process parameters such as pressure pulse amplitude and duration, laser spot size or sacrificial overlay.Among other results, simulations confirmed that the affected depths increased with pulse duration, peak pressure and cyclic deformations, thus reaching much deeper layers (> 0.5 mm) than with any other conventional surface processing. To improve simulations, the use of experimental VISAR determinations to determine pressure loadings and elastic limits under shock conditions (revealing different strain-rate dependences for the two stainless steels considered) was shown to be a key point.Finally, the influence of protective coatings and, more precisely, the simulation of a thermo-mechanical uncoated laser shock processing were addressed and successfully compared with experiments, exhibiting a large tensile surface stress peak affecting a few tenths of micrometres and a compressive sub-surface stress field.

Analyses of shock waves and jams in traffic flow

Abstract: In this paper, we study the certain qualitative properties of a new anisotropic continuum traffic flow model in which the dimensionless parameter or anisotropic factor controls the non-isotropic character and diffusive influence. We discussed the travelling wave solution for our model and find out the condition for the shock wave. Shock and rarefaction waves are obtained from the new model and are consistent with the diverse nonlinear dynamical phenomena observed in a real traffic flow. However, our model for large values of anisotropic parameter removes the discontinuity as pointed out by Berg et al (2000 Phys. Rev. E 61 1056). The nonlinear theory of the cluster effect in a traffic flow i.e., the effect of appearance of a region of high density and low average velocity of vehicles in an initially homogeneous flow, is also discussed. It is shown that an appearance of a localized perturbation of finite amplitude in the stable homogeneous flow can lead to a self-formation of a local cluster of vehicles. It is also been observed that the cluster effect from our model shows a good agreement with the results of Kerner and Konhauser (1994 Phys. Rev. E 50 54) and Jiang et al (2002 Trans. Res. B 36 405).

Interplanetary flow systems associated with cosmic ray modulation in 1977–1980

Abstract: The hydromagnetic flow configurations associated with cosmic ray modulation in 1977 to 1980 were determined using solar wind plasma and magnetic field data from Voyagers 1 and 2 and Helios 1. The modulation was related to two types of large scale systems of flows: one containing a number of transients such as shocks, post shock flows and magnetic clouds; the other consisting primarily of a series of quasi-stationary flows following interaction regions containing a stream interface and often bounded by a forward reverse shock pair. Each of the three major episodes of cosmic ray modulation was characterized by the passage of the system of transient flows. Plateaus in the cosmic ray intensity time profile were associated with the passage of systems of corotating streams.

Shock Waves and High-Strain-Rate Phenomena in Metals. Concepts and Applications.

Abstract: : The subject matter addressed by the chapters which compose this book is organized into nine sections followed by a number of appendices. Section 1 consists of a Historical Perspective followed by sections on High Strain-Rate Deformation, Dynamic Fracture, and Adiabatic Shearing (2,3,4). The next three sections deal with shock waves and constitute the core of the book: Shock Waves I: Experimental Techniques, Shock Waves II: Fundamentals, and Shock Waves III: Microstructural and Mechanical Effects, (5,6,7). The last two chapters treat the major applications: Dynamic Compaction of Powders (8) and Explosive Metal Working and Welding (9).