A modified split hopkinson torsional bar in studying shear localization

A modified split Hopkinson torsional bar (SHTB) is introduced to eliminate the effect of the loading reverberation of the standard SHTB on the study of evolution of shear localization. The effect, the cause and the method by which to eliminate loading wave reverberation are carefully analysed and discussed. By means of the modified apparatus, the post-mortem observation of tested specimens can provide data on actual evolution of micro-structure and micro-damage during shear localization. Some test results of shear banding conducted with this apparatus support the use of the modified design. Moreover, the modification makes possible the correlation of evolving micro-structures to the transient shear stress-strain recording.

Elimination of loading reverberation in the split hopkinson torsional bar

The loading reverberation is a multiple wave effect on the specimen in the split Hopkinson torsional bar (SHTB). Its existence intensively destroys the microstructure pattern in the tested material and therefore, interferes with the study correlating the deformed microstructure to the macroscopic stress-strain response. This paper discusses the problem of the loading reverberation and its effects on the post-mortem observations in the SHTB experiment. The cause of the loading reverberation is illustrated by a stress wave analysis. The modification of the standard SHTB is introduced, which involves attaching two unloading bars at the two ends of the original main bar system and adopting a new loading head and a couple of specially designed clutches. The clutches are placed between the main bar system and the unloading bars in order to lead the secondary loading wave out of the main bar system and to cut off the connection in a timely manner. The loading head of the standard torsional bar was redesigned by using a tube-type loading device associated with a ratchet system to ensure the exclusion of the reflected wave. Thus, the secondary loading waves were wholly trapped in the two unloading bars. The wave recording results and the contrasting experiments for examining the post-mortem microstructure during shear banding both before and after the modification highly support the effectiveness of the modified version. The modified SHTB realizes a single wave pulse loading process and will become a useful tool for investigating the relation between the deformed microstructure and the macroscopic stress-strain response. It will play an important role especially in the study of the evolution of the microstructure during the shear banding process. (C) 1995 American Institute of Physics.

Are Bar Associations Anticompetitive? An Empirical Analysis of Recommended Prices for Legal Services in Spain

The European Commission Report on Competition in Professional Services found that recommended prices by professional bodies have a significant negative effect on competition since they may facilitate the coordination of prices between service providers and/or mislead consumers about reasonable price levels. Professional associations argue, first, that a fee schedule may help their members to properly calculate the cost of services avoiding excessive charges and reducing consumers’ searching costs and, second, that recommended prices are very useful for cost appraisal if a litigant is condemned to pay the legal expenses of the opposing party. Thus, recommended fee schedules could be justified to some extent if they represented the cost of providing the services. We test this hypothesis using cross‐section data on a subset of recommended prices by 52 Spanish bar associations and cost data on their territorial jurisdictions. Our empirical results indicate that prices recommended by bar associations are unrelated to the cost of legal services and therefore we conclude that recommended prices have merely an anticompetitive effect.