Influence of dissipated energy on shear band spacing in HY100 steel

To analyze the formation of multiple shear bands in HY100 steel, we consider an infinitely extended layer of finite thickness subjected to shear loading. The perturbation approach, associated with numerical methods, is used to determine the instability modes. The criteria of Wright-Ockendon and Molinari are used to determine the shear band spacing. The effect of each material parameter on the shear band spacing is determined by using a power law constitutive relation. The Johnson Cook model is used to illustrate the influence of the constitutive relation on the results of the adiabatic shear band spacing, by studying the response of HY100 and comparing with available experimental and power law results over a very wide range of strain rates . In this study, we show that the variation of the Taylor-Quinney parameter, as a function of shear strain is an important parameter that plays a significant role in the calculation of the shear band spacing

Influence of dissipated energy on adiabatic shear band spacing: influence de l'énergie dissipée sur la formation des bandes de cisaillement adiabatique multiples

International audienc

Triggered breakdown in low-pressure hollow cathode (pseudospark) discharges

Triggered breakdown in hollow cathode discharges in geometries similar to those used for pseudospark switches and pseudospark pulsed electron beams has been investigated experimentally and with a two-dimensional model previously developed. A systematic study of the influence of the discharge conditions (applied voltage and pressure), geometry, and trigger conditions (trigger intensity and position) on the time to breakdown in helium is presented, and some data are also shown for argon. Excellent qualitative agreement is found between the model predictions and the experimental results. The relation between the time to breakdown and the geometrical distribution of injected charge is discussed, and the understanding gained from these model results is used to suggest guidelines for trigger optimization. Conditions wherein significant oscillations in the currenta "current quenching'' effectare observed in the prebreakdown current wave form are discussed.Pages: 77-8