An Empirical Method of Dispersion Correction in the Compressive Hopkinson Bar Test

The dispersion of longitudinal stress waves as they propagate in pressure bars distorts the shape of the pulse, and so can be a limitation to the accuracy of high strain rate tests such as the compressive split Bopkinson pressure bar (SHPB). The method of dispersion correction described in this paper is based on a bar phase characteristic which is derived entirely from measured stress pulses generated by the elastic Impact of small spheres. This method does not depend on any theoretical model of wave propagation, and automatically includes all distortions that could arise in mechanical or electronic aspects of the test. It is quick and convenient enough to be used on a routine basis to improve the accuracy of SHPB tests. RbumC : La dispersion des ondes de conuainte longitudinales transportkes dans des barres deforme l'impulsion, ce qui peut restreindre la precision des essais grande vitesse de deformation, tels que ceux rkalises i la barre d'Hopkinson en compression. Les modalites de la correction de la dispersion dkcrites dans le present article sont fondees sur des caracteristiques de phases derivees entikrement d'irnpulsions mesurkes, crCtSes par I'impact Clastique de petites spheres. Cette methode ne depend d'aucun modele theorique de propagation d'ondes, et prend automatiquement en compte toutes les erreurs possibles dues aux aspects mecaniques ou klectroniques de I'essai. Elle est suflisamment rapide et facile pour @ue u ~ i l i d e regulibrement afin d'ameliorer la precision des essais 2 la barre d'Hoplunson.