J. de Fouquet

Pics de frottement intérieur à très basse température sur le titane et le zirconium écrouis

SummaryThe following study deals with internal-friction measurements made on zirconium and titanium in the very-low-temperature range in longitudinal vibrations at about 30 kHz. New relaxation peaks have been observed after cold-working at 300 K. Their main caracteristics are compared with those of all the different cold-worked peaks of these two metals from 4.2 to 370 K.RiassuntoNello studio seguente si trattano le misure di attrito interno effettuate su zirconio e titanio nel campo delle bassissime temperature in vibrazioni longitudinali a circa 300 K. Si sono osservati nuovi picchi di rilassamento dopo una lavorazione a freddo a 300 K. Si confrontano le caratteristiche di questi picchi con quelle dei diversi picchi di lavorazione a freddo di questi due metalli da 4.2 a 370 K.

VACUUM EFFECT ON FATIGUE CRACK PROPAGATION AT LOW RATE

ABSTRACT Crack closure measurements were made during fatigue crack growth at low rates and near threshold conditions in air and in vacuum on a 2618 T651 Aluminium alloy. The techniques used to detect crack closure were the compliance variation and the potential drop techniques. The results obtained suggest a definition of the effective stress intensity factor taking into account both the effects of the load ratio and of the environment.